Census 2000: Counting on GIS
As the population of the United States has steadily increased, the U.S. Census Bureau has come under fire for its mistakes in the population count. Undercounts and a general overlooking of immigrants, the homeless, low-income families and even children have contributed to the depth of error in census figures.
Mistakes were widely noticed in the 1990 census, in which 8.4 million people were not counted, and 4.4 million people were double-counted because of dual residences or census errors. In addition, only 65 percent of survey forms were returned, allowing only partial results of the 1990 census to be delivered on schedule, and costing additional time and money to complete the process.
The population count is directly used to apportion seats in the House of Representatives, to distribute federal funds and to set policies. In addition, research groups and businesses depend heavily on demographics derived from census data for market information. Many local governments felt cheated after the 1990 census, having missed out on their fair share of federal grants, and they contested the figures. Few have been successful in their disputes, but the discrepancies brought attention to the widespread problem of undercounts by the bureau and have boosted local involvement and the use of technology in the survey process.
Fighting the numbers Jessica Heinz, Los Angeles assistant city attorney, participated in litigation efforts after the 1990 census, in which Los Angeles was undercounted by 3.8 percent and lost millions of dollars in federal funds. Heinz attributed the undercount to the high number of immigrant families in California who were not counted or did not fill out the form correctly or completely.
“Major decisions are being made in terms of transit and funding, based on census data,” says Wayne Bannister, urban research manager for the Chief Administrative Office in Los Angeles County. “A lot of money is distributed according to the population. It’s important to be as [accurate] as possible.”
At the time of the 1990 census, Los Angeles did not employ technology like it does today and thus relied on records from the U.S. Postal Service, utility meters and statistical sampling to complete its own population count. The city lost its case because the Supreme Court upheld the Census Act, which states that the secretary of commerce has discretion in regard to sampling.
“It’s frustrating for California because we bear a lot of the brunt of immigration,” Heinz says. “We have a lot of people to take care of.” Los Angeles is currently participating as a defendant in a lawsuit filed by the House of Representatives in response to the bureau’s decision to use sampling techniques in the 2000 census.
Long Beach, Calif., also experienced a loss after the 1990 census. The city contested the figures, which were undercounted by 18 percent, or roughly 21,500 citizens.
The city, which uses GIS across departments, performed field surveys to conduct its own census. Jack Humphrey, advance planning officer and census 2000 coordinator for the city, attributes the discrepancy to the high concentration of immigrants who did not fill out their forms or respond to field workers.
Humphrey says the city demanded a recount, specifically pointing out neighborhoods with high concentrations of immigrants and homeless. The bureau did not perform the recount, and the city estimates that it lost $10 to 15 million in federal grant money for health and transportation projects. “It’s important that we have everybody counted that we’re entitled to have counted,” he notes.
Humphrey now is involved in litigation to support statistical sampling nationwide. “The predictions are that, without sampling, this will be the worst census ever,” he says.
Ontario, Calif., noted questionable figures in its 1990 post-census review and disputed the census’ numbers. Prior to the 1990 census, the city had conducted its own field survey using paper maps. The information was converted to digital maps, and the city has regularly updated the records and advanced its technology ever since.
The original data was based on utility meter records and postal records that were placed in a GIS. Problems with the census count occurred with regard to illegal or modified units, such as basement apartments, secondary units such as trailers on a one-unit lot, or divided houses such as duplexes. The city’s maps proved to be accurate, and the census made the necessary corrections.
“We want as much money as we can get. If there are units here, we want them to be represented,” says GIS Project Manager Elliott Ellsworth.
GIS vs. census GIS has played a key role in disputes regarding undercounts because it provides detailed data not available from other sources. “A lot of people challenge the census,” says Chris Thomas, state and local government market manager for ESRI, Redlands, Calif. “The Census Bureau basically says, ‘You need to show us specifically where the errors are,’ and that’s where GIS comes in. You can show the patterns and the addresses. GIS [gives you] a voice with the census.”
Los Angeles, like Long Beach, employs a wide variety of technology to keep its own address records and population figures up to date. The city primarily uses ArcInfo and ArcView GIS technology from ESRI, but it still depends on city records of utility meters, sanitation, trash pickups, new construction and postal addresses to maintain the GIS.
The city also has delved into aerial photography and GPS collection. The different data can be merged into a database and compared with the census data, says city Program Analyst Dennis Moody.
The same technology could easily be implemented at the bureau, he adds. Aerial photography also would eliminate the need for excessive field work. “[The Census Bureau] does a lot of field work just to verify what we’re telling them [with GIS],” Moody says.
Long Beach has experienced dramatic population shifts resulting from the recent closing of a U.S. Navy port and its surrounding housing. The dramatic drop has rendered the city’s 1990 census data obsolete, according to GIS Project Manager Tina Dickinson, who says she would like to see updates more than once every 10 years.
While GIS projects have helped Long Beach to keep current geographic data within the city, the census data still is outdated. “There needs to be a mechanism [by which] local agencies can communicate the [geographic] information to the census bureau to help them out and to keep current data,” she says.
In 1996, the city performed its own population estimate with ethnic breakdowns to re-evaluate the council districts. The city created a GIS application in which council members could review the blocks and potential scenarios for redistricting. Within one week, each district had a new geographical plan reflecting the new population numbers. The same program was used for consolidating the precincts and for voting sites. “We couldn’t have done this [project] with this speed, and we couldn’t have produced as many ‘what-ifs,’ without GIS,” Dickinson says.
Compatibility issues GIS is used in many capacities throughout cities and counties, and, although some groups are able to send data to the bureau electronically, not all systems are compatible with its database. “An increasing number of entities are going to GIS systems and digital files,” says Nancy Bechler, supervisory geographer in the Atlanta regional office of the U.S. Census Bureau. “They’re great when we can get them, but they don’t always contain the same information that we need, or they are not compatible with our systems. A lot of times it’s easier to work with a paper source.”
Rural areas almost always offer only paper resources. “When you get out to something like Coffee County, Ga. [pop. est. 32,000], these people aren’t going to know what a GIS is, so there’s very little hope of a digital file,” Bechler says. “We’re doing good to find anything that shows us address breaks for some of the more rural areas.”
“There are ways the bureau could work with regional agencies to help define programs and formats to collect information electronically,” says Terry Bills, managing principal planner for the Los Angeles-based Southern California Association of Governments (SCAG). The group acts as a regional planning organization and provides GIS software, data and training in five counties and 184 cities in California. “The frustration is that there is a fair number of jurisdictions that could send back forms electronically. I’m not sure the bureau has moved as aggressively as it could to move to an electronic format.”
Conducting the census The current method for conducting the census, according to the 14th Amendment to the Constitution, calls for “counting the whole number of persons in each state.” To accomplish that, the census bureau relies on its 1990 computerized records and performs numerous rounds of updates to account for new addresses, construction and other geographical changes. Urban addresses receive survey forms by mail; rural addresses usually require a visit from a field worker.
“It is a massive effort I’m not sure all of us appreciate,” Bills says. “Trying to get all of the geography and all of the boundaries right is a daunting and quite difficult task for the bureau to deal with.”
The census process follows five steps: 1. Updating the TIGER file. Since 1995, workers in 12 regional offices across the United States have performed cleanup work on the existing census database, known as the Topologically Integrated Geographic Encoding and Referencing (TIGER) file.
The file, which was created for the 1990 census, contains maps for each city, county and state and includes all roads, rivers, railroads, political boundaries and other geographical data. Census workers are responsible for correcting street names, adding new streets, adding new boundaries and otherwise cleaning up the TIGER file. The staff also works on the Master Address File (MAF) to include new addresses and verify current listings.
The bureau obtains most of the information for TIGER and MAF from the U.S. Postal Service, but it receives additional data from cities, counties, regional planning offices or 911 units. Workers compare new data with the 1990 files, and any item that does not match or is missing comprises the workload. The staff researches the item and adds new information to the files.
The bureau’s regional office in Atlanta covers Georgia, Florida and Alabama, and 40 staff members work in two shifts from 7:30 a.m. to 12:30 a.m. to correct the TIGER and MAF files. Staff members work on an assigned area, such as a county, and they may be required to work on a single area for weeks or months at a time. Dade County, Fla., which includes Miami, required a little more than a year of work, Bechler says.
Surprisingly, workers also use a number of commercial sources such as atlases and store-bought road maps to obtain geographic information. “These [books] don’t provide address information, but they very frequently will show you all kinds of roads that aren’t appearing in TIGER, and they almost always will have an index to help you find the road,” Bechler explains. “A lot of the stuff that we receive directly from the counties won’t have an index, which makes life a little bit tougher.” Once the TIGER files are updated as much as possible, the workload turns to preparations for field work.
2. Creating assignment areas for field work. Unlike large urban areas, where nearly every address is in traditional city style (i.e., 100 Main St.), rural areas may use post office boxes or atypical addresses. Field workers drive within an assigned area to obtain the addresses and correct the census maps.
Workers set up the assignment areas in reasonable sizes based on 1990 data. In areas with open land and relatively few people, such as Montana, the assignment area may be 150 square miles, while in an urban area it may be only 10 square miles.
Weather plays a role in the time of the assignment as well. “When we do field work, we try to set it up so that New England [workers are not] going out in the dead of winter running up and down the street looking at addresses,” Bechler explains. Once the assigned areas are planned, the regional office prints paper maps to be distributed to the field workers.
3. Performing field work and correcting the database. Each field worker receives a locator map with the assigned shaded area; an assignment area map that shows the census blocks; maps for each census block; and an address register book. The worker drives in a pattern around the block, notes anything that is not shown on the map and records the corresponding addresses. The maps and address book are then sent back to the regional office, where the corrections are input and the maps are digitized.
The process may require several visits. Some houses may not have addresses marked on their mailboxes, and field workers may be unable to locate the residents to make inquiries.
4. Mailing forms and performing personal field visits. Once the address list is corrected and completed, the mailing process begins. The bureau relies on the mailout/mailback process to confirm about 80 percent of all addresses in the country. The remainder of the addresses require a field visit, in which a field worker must distribute the forms or sit down with residents to complete the form together.
A major problem occurred with the 1990 census when people failed to return the forms, requiring costly, sometimes unsuccessful, field visits. To combat the problem of missing forms, the Census Bureau, backed by the Clinton Administration, has proposed using statistical sampling to collect the remaining data.
Sampling is favored by many local users as an effective means for the bureau to fill in holes in the returned forms, but it has faced opposition in Washington, D.C., this year. In August, a three-judge panel ruled that sampling was unconstitutional, and the measure was headed to the Supreme Court following an appeal.
Sampling, which is a product of science, has become a political tool, backed by Democrats and opposed by Republicans, who fear that sampling may recognize more immigrants and minorities who are, traditionally, Democrats. The “virtual Democrat” has propelled many Republicans to reject sampling, Bannister says.
Nevertheless, local governments and census data users generally seem to favor sampling. “There’s no way to conduct the census without using any type of sampling,” L.A.’s Heinz says. “The only way to correct the undercount is to use the dual system.”
5. Processing and delivering the data.
In processing the completed/returned forms, the bureau is using a digital data capturing system. The system digitally scans each form and converts it into a computer-readable format. Hand-written marks will be deciphered using intelligent character recognition tools. Some staff may still be required to manually type in responses, but the majority of data will be read digitally.
Once the information has been processed, the secretary of commerce is required to deliver state population counts to the president by Dec. 31, 2000. The bureau provides census tabulations to the states by April 1, 2001, and the tabulations then can be used to reapportion the seats in the House of Representatives and to redistrict state and local elections. The results also are available to companies or other organizations who regularly use census data for research or other business purposes.
Impact of census data Although the census was created with a distinct political purpose, many organizations have taken advantage of the existing figures for other tasks, such as petitioning for the establishment of branch libraries and parks. Research groups use the numbers to track migration patterns and changes; genealogists trace individual families using census numbers; and corporations use the data to make decisions about where to build factories and stores, where to market products, how and where to advertise, and in gauging potential success in a given area.
An accurate census will ensure proper governmental representation and fair allocations of federal grant money, as well as usable data for multiple organizations. Because census data has widespread applications, it is important to have the most reliable figures.
For years, GIS technology has assisted local governments in obtaining information quite similar to that used at the Census Bureau. It has produced the opportunity for partnerships between the bureau and technology experts who can introduce census workers to more efficient ways to obtain and decipher their data. And it has provided an opportunity for local governments to take a more active role in a process that affects them so deeply.
When the Vermont Agency of Transportation (VAOT) started placing its GIS-based maps on the Internet, the purpose was to streamline operations for the VAOT staff. The technology allowed the staff to work more efficiently and permitted residents to access information on their own instead of calling the VAOT directly.
“We’ve been able to create a network that provides our staff with more comprehensive information more quickly and efficiently,” says Tom Hurd, VAOT information systems manager. The staff has published GIS-based maps on the Internet since April 1997 using a software package from Intergraph, Huntsville, Ala.
To create the GIS, an inventory of the state’s roads was needed. Using orthophotography, more than 13,000 miles of interstates, highways and municipal roads were digitally mapped and inventoried.
Airports were the next dataset created for the project. The VAOT web site (www.aot.state.vt.us) displays vector-based maps that show the locations of the 16 different airports in Vermont. Users query by airport name, which produces a map of the facility’s location and other corresponding information, such as what type of airport it is, who owns it, its latitude and longitude, and its runway lengths and types. Aerial photos of some of the airports are available for viewing.
Consultants accessing VAOT’s web site can obtain geodetic survey information, such as height, latitude and longitude. Previously, they had to call surveyors to acquire the data. Now, users can search the web site by county or town, and the system generates a map showing all recorded survey monuments in the area of interest. Placing the information on the Internet frees VAOT staff members from the phone and gives them time to work on other projects.
The amount of data in the GIS grows daily, as does the number of potential applications for the data, Hurd says. “The GIS will allow us to plan more efficient and environmentally sensitive designs,” he says. “In planning road developments, we’ll query the database to identify wetlands, hazardous waste or other areas that would prohibit us from building a road through certain regions.”
Planning with the GIS, however, has not been confined to just road developments. VAOT’s planning department last year acquired GIS software tools that allow users to collect and analyze vehicle load volume data (i.e., how much weight each bridge or road can withstand). The data will be used in an operational program to route trucks carrying a certain weight over the appropriate bridges or roads. In the event of an emergency, such as a bridge collapse, the program will help re-route traffic.
Construction projects also will be maintained and managed using the GIS. Field crews that identify roadways with deficiencies can tag them in the GIS for improvement projects. Those projects can then be prioritized. Once construction is under way, VAOT personnel can easily monitor the progress of the projects with the GIS.
The VAOT plans to give the same monitoring tool to the residents. By accessing the agency’s web site, interested parties can get information about proposed or on-going road construction, including locations, corresponding detours, road closures or hazards associated with the projects.
This article was written by Mary Jo Wagner, a London, England-based freelance writer.
In Loudon County, Tenn. , southwest of Knoxville, city and county officials have launched a joint program to perform aerial mapping and build geographic information system (GIS) databases. Sharing expenses has saved local taxpayers almost $500,000.
The project involves the Loudon and Lenoir City utility districts and Loudon County. The mapped area spans 284 square miles, and the maps include property boundaries, subdivision lines, buildings and roads.
The entities split expenses, each paying one-third of the cost, and the area’s 911 emergency services agency reimbursed the county for part of its tab in exchange for access to the maps. Continental Aerial Surveys, Alcoa, Tenn., spearheaded the effort to create the project.
Ben Bonfoey, a substation engineer at the Lenoir City Utility Board, says that it was easy for departments to share information because they agreed to adopt compatible hardware and software systems. “Building compatible systems laid the groundwork for us to share information with each other and with neighboring counties and districts,” he says. “This project allowed us to tie into their database and build an integrated regional system.”
In building the local database, images were captured on black-and-white aerial film, converted from negative to positive images and scanned into a digital format. A fine-grain Kodak film allowed for small details when the images were captured for digital use. Specific information, such as property boundaries, rights of way, utility lines and addresses was added. All the data resides in layers that can be turned on and off as needed.
When the new system was fully implemented this year, the participating governments saw several immediate benefits. For example, construction companies are now able to access maps with all utility lines, eliminating the need for cable, telephone and water crews to rush to construction sites to mark them. Additionally, it is much easier for utility crews to locate specific problems and for emergency personnel to respond to citizens.
Loudon County recently relied on the new maps to oppose a claim by a landowner that standing water decreased his land’s value. “The citizen brought pictures of standing water to substantiate his claim,” Property Assessor Doyle Arp reports. “However, we used topographic information to prove that the water was created by runoff during wet weather and quickly drained away. Therefore, it was not damaging his land or affecting its value. Without these maps, it would have been our word against his photographs.”
Berry adds that detailed aerial maps and databases allow city and county planners to balance future growth against the desire to preserve the area’s natural beauty. “We are in the foothills of the Appalachian Mountains. Residents want to promote economic development without destroying the ecosystem that makes this area an attractive, enjoyable place to live,” he says. “Cities and counties all over the country are struggling with these same issues. Officials need detailed information, in a flexible digital format, to wisely manage growth.”
The idea of establishing GIS capabilities within small municipal agencies has, for some agencies, been mere wishful thinking because of ever-tightening funding for technology. Now, with Y2K “millennium bug” considerations looming closer on the horizon, spending money on traditional high-end GIS software and workstations has become even more of a back-burner item for many organizations.
But, one municipality in northern Colorado has found a way to provide GIS services to its employees at a low cost. Loveland has created an award-winning GIS, known as the Loveland Geographic Information/ Cartographic (LOGIC) System, that is based upon desktop PC technology. The LOGIC System is unique in its integration of GIS and computer-aided drafting (CAD).
Loveland uses a combination of San Rafael, Calif.-based Autodesk’s AutoCAD Map 3.0 and Redlands, Calif.-based ESRI’s ArcCAD forAutoCAD 13 and ArcView 3.0a software. All PCs in the city used to develop data run Microsoft’s Windows NT Workstation 4.0. Users of the LOGIC System run either Windows NT Workstation 4.0 or Windows 95 on a variety of PCs. The system has given Loveland the best of the CAD and GIS worlds, according to Steve Holmes of the city’s Land Records Management (LRM) Division. Integrating CAD and GIS provides the city with a complete spatial analysis system along with traditional CAD functionality. That has meant lower hardware and software costs as well as greater flexibility.
The LOGIC System is used by many city departments, including Water and Power, Long-range Planning, Engineering, Parks and Recreation, Sales Tax Administration and in the city manager’s office. Along with traditional data sets such as parcels and zoning districts, the LOGIC System has complete utility data (water, wastewater, stormwater and electric) and planimetric data (buildings, streets, driveways, curbs, canals, etc.). The police and fire departments also are using LOGIC system data in their new computer-aided dispatch system.
The LRM Division coordinates GIS on a city-wide level and also provides GIS services to departments and divisions without GIS capabilities of their own. The applications developed by city staff range from a traditional mailing label routine, based upon pre-defined or user-entered search radii, to calculating reimbursements of storm drainage impact fees for land developers based upon building permits. One of the newer applications calculates the population of Loveland (48,270) based on utility billing information and census tract densities.
For large municipalities and businesses, a desktop solution for GIS may not be feasible, Holmes says. However, for small communities and businesses, the integration of CAD and GIS on the desktop allows a group to keep costs down. That helps in competition with other departments for funding.
This year, Loveland was honored by the Urban and Regional Information Systems Association (URISA) with the Exemplary Systems in Government (ESIG) Award in the small municipality category (cities with a population under 100,000). Chicago-based URISA is an organization of public and private sector spatial data management professionals. The ESIG award provides international recognition of exceptional achievement in the application of information technology that improves both the delivery and quality of government services.
Norfolk, Va., has a rich cultural and historical heritage and a rapidly aging infrastructure. As part of the city’s effort to modernize its infrastructure management, the Department of Utilities currently is implementing a comprehensive, integrated management system (IMS) and GIS in a $1.3 million, three-phase project.
By implementing technology to manage its aging infrastructure, the department not only will be able to serve its residents and tourists, but also will stay ahead of competitive pressures and meet or beat regulatory requirements. Once fully implemented, the systems will give the city quantifiable management information for everything from capital budget approval from the city’s elected leadership to tracking operations and maintenance expenses.
The first phase of Norfolk’s implementation demonstrates why fully leveraging technology is critical in a utility and local government operating environment. The department is completing a $100 million water treatment plant upgrade to provide clean water for Norfolk, as well as for neighboring Virginia Beach and for the U.S. Navy, whose largest base is in Norfolk.
As part of the agreement under which Norfolk provides water to those customers, the city must provide accurate and timely O&M expense tracking data. To do that, the city is using the V7/Plant IMS from Hansen Information Technologies, Sacramento, Calif. The system, which was fully implemented in August 1997, also will be used to manage all of Norfolk’s water utility assets, including its distribution system.
Integrated with Redlands, Calif.-based ESRI’s GIS solution, Arc/Info, the system will enable the city’s management staff to access all geographic data. The department currently is in the process of converting the necessary data and expects the project to be completed in November 1999.
Historically, the city has relied heavily on the experience of field personnel to assess the need for maintenance. However, that process can be imprecise. The use of integrated IMS/GIS will enable the city to use accurately documented maintenance histories for budgeting, scheduling of preventive maintenance and staff planning.
Additionally, the GIS element of the integrated system will enable spatial analysis of the city’s infrastructure. In an older, historic city such as Norfolk, that can be especially critical in maintaining a water system that has been repaired repeatedly.
For its residents, the city will be delivering higher levels of service. For instance, automated customer service and work order systems are expected to yield quicker response times to customer problems. Additionally, regularly scheduled preventive maintenance should greatly reduce the probability of delivery problems.
While the city has consistently met regulatory requirements (Clean Water Act, Drinking Water Act, etc.), improved documentation of its processes will make compliance easier in an era of increasing regulation. Better documentation and high-tech systems also assist with overall management of an aging infrastructure.
This article was written by Sheila Smith, utilities planner for Norfolk’s Department of Utilities.
By outsourcing some of its workload to private companies, the U.S. Census Bureau has been able to incorporate GIS and digital technology into its operations and take advantage of many efficient technology programs.
In May, for example, the bureau partnered with GeoResearch, Bethesda, Md., to improve its TIGER database. The company is creating a customized version of its GeoLink software, which uses satellite-based GPS technology to obtain the geographic coordinates of residential addresses. The software conforms to the current TIGER formats.
Field workers will carry satellite receivers to pick up GPS coordinates and feed them into the maps. The workers also can add information, such as street names or geographical elements, to the maps.
This past summer, the bureau signed a deal with ESRI, Redlands, Calif., and IBM, Armonk, N.Y., for development of the Bureau’s Data Access Dissemination System (DADS). The program will allow the public to create customized reports with census data. Users will be able to access DADS from the Web to query geographic, demographic and economic data and to generate maps. The system is an efficient way to transmit data to residential users as well as to congressional personnel.
The bureau also has enlisted Bethesda, Md.-based Lockheed Martin to develop new methods of processing the returned survey forms with digital capturing technology. Company tests indicate that about 80 percent of the forms will be read digitally.
Outsourcing to companies with expertise in certain areas of technology will increase the likelihood of accurate maps. While the companies are required to conform to the bureau’s current formats, the introduction of new technology opens the door for widespread use of better technology within the Census Bureau’s operations.
To further the goal of providing accurate data, the U.S. Census Bureau has enlisted the services of local governments. By using the local groups’ GIS technology and personal knowledge of the municipality, the bureau hopes to produce more correct counts and maps.
The bureau also hopes that, by allowing participation from locals, it will avoid future disputes regarding the final figures. Cities can contribute figures to the census-taking process through several programs. For example:
* The Local Update of Census Addresses (LUCA) is a result of the Census Address List Improvement Act of 1994, which recognized the inaccuracies in previous surveys and directed the bureau to form partnerships with local governments to create more precise address lists and maps for the 2000 Census. Cities and counties can use their own technological methods to provide counts to the bureau.
* The Address List Review portion of LUCA allows local groups to correct the address lists before the 2000 forms are even mailed. Participating governments receive paper address lists or CD-ROMs.
For the 1990 census, local officials had the opportunity to review lists, but they were limited to 15 days. Now, during a three-month review period, local officials can add new residential addresses, delete addresses that no longer exist and make any other necessary corrections. They also can note specific areas believed to have been overlooked in the 1990 census. The bureau then reviews the corrected files and will discuss discrepancies with the local group. Participation in the review process is voluntary.
* The bureau also has initiated Complete Count Committees in cities to promote awareness of Census 2000 in local communities and encourage residents to complete survey forms and return them to the bureau. Promotional activities include news conferences, advertising, distributing educational materials, making telephone calls and attending public meetings. The committees are encouraged to partner with schools, churches, foundations, sports programs or other entities to relay the importance of completing and returning the form.
By directly participating in census survey activities and using their own survey methods, local governments increase their chances of having an accurate count. Educating residents further increases the probability of an accurate census.