Memorandum

City of Lawrence

Planning Department

 

TO:

Dave Corliss, Interim City Manager

Debbie Van Saun, Assistant City Manager

FROM:

Planning Staff

CC:

Sheila Stogsdill, Acting Planning Director

Date:

8/7/06

RE:

Population Projections and Estimates

 

I. Introduction

 

Staff prepared a memo on July 14, 2006 that discussed best practice methods for population projecting and estimating by local governments.  The results of research by Staff showed the methods used by the Planning Department are methods that are used all around the country.  The July 14, 2006 memo also talked about Staff’s early efforts at testing Census population estimates for Lawrence and Douglas County.  Staff has completed that task and this memo provides the results of those tests. The first section of this memo outlines the methods used by the U.S. Census Bureau for population estimates and outlines their latest results. The second part of this memo outlines the city estimates, using utility records and building permit data, and the third section details problems other cities have had with the Census estimates. A recommendation for further steps completes the memo.

 

II. Census Estimates

 

A. Method:

The Census Bureau releases estimates of population annually every July 1st. The estimates are used for the allocation of many resources, including community development block grants and federal and state transportation fund money. In addition, the estimates are used in the calculation of key figures for the city, and county, such as unemployment rates, inflation numbers, and other economic indicators. These estimates are developed in cooperation with the Federal-State Cooperative Program for Local Population Estimates (FSCPE). In the state of Kansas, the agency that is a part of that cooperative program is the Division of the Budget.

According to Census publications, a formula combining the census and administrative records information are used to produce current population estimates consistent with the last decennial census counts for the county as a whole. This method is referred to as a component of change population method. The Federal agencies provide tax records, Medicare records and some vital statistics information. The FSCPE agencies supply state school enrollments, vital statistics, and information about group quarters like college dorms or prisons.

Sub-county population estimates are then produced using a Distributive Housing Unit Method that uses housing unit change to distribute county population to sub-county areas.  The Census Bureau develops a household population estimate by applying the occupancy rate and average persons per household (PPH) from the latest census at the sub-county level to an estimate of housing units.  The non-household population is measured by the change in the group quarters population.  The final estimate is then produced by adding the population in group quarters to the household population.

With each new issue of July 1 estimates, the population estimates program revises estimates for years back to the last census. Previously released estimates are superseded. Revisions to estimates are usually due to revised or updated administrative input data, changes in methodology, or legal boundary changes, especially for sub-county units of government, such as incorporated places.

B. Estimates:

 

Population estimates released by the Census Bureau in July of 2006 put the City of Lawrence’s population at 81,816 people as of July 1, 2005. This represents only a gain of 1,718 people since the Census of 2000. In addition, Douglas County’s population is estimated to be 102,914 people as of July 1, 2005, a gain of 2,952 people since the Census of 2000.

 

 

C. City Estimates:

 

The City of Lawrence has employed a method for estimating the City’s population that utilizes building permit data, demolition data, average household size, and vacancy rates. In addition, staff has studied data from water utility records in an effort to solidify the current practice of estimating population based on building permits.

 

Building Permit Method:

 

Our local population projection is derived from the housing unit method.  It involves totaling the number of new residential dwelling units constructed each year since the 2000 Census; subtracting the number of dwellings that were demolished during the same time period to derive the total number of new dwelling units built since the 2000 Census period; then, multiplying the number of new dwelling units by the 2000 Census vacancy rate for the city to establish the number of new occupied dwelling units.  Then the total number of occupied dwelling units is multiplied by the average number of persons per household, based upon the 2000 Census, to derive a figure for the new population residing in the new dwelling units.  Finally, this new population increase is added to the 2000 Census population to establish a new estimate for the City's population.  Our estimating period runs with the calendar year so each year’s estimate reflects the building permit activity for the full 12-month period.

 

Using this method, there are an estimated 89,643 people living in the City of Lawrence as of January 1, 2006.

 

 

Staff has also studied the different effects that a decreased average household size, and an increase in vacancy would have on the above population estimates. The above figures represent a vacancy rate of 4.2% (or an occupancy rate of 95.8%), and an average household size of 2.3 people, both of which came from the 2000 Census. The below table illustrates the effects of adjusting the vacancy rate and average household size since the 2000 Census, on the population estimates of January 1st, 2006.

 

 

If the vacancy rate was raised to 15% and the average household size decreased to 2.1 people, building permit data still shows a 2006 population estimate of 88,169 people.

 

 

Utility Record Method:

 

The City of Lawrence tracks water usage by sales volume, as well as by number of active accounts. According to records, 3,612 residential accounts and 34 multi-family accounts have been added from 2000 to 2005.  Those figures do not include usage by the University of Kansas or Haskell Indian Nations University. The University of Kansas estimates that 4,906 students resided on campus in 2005, a decrease of 248 people from 2000. University populations were included in the Census 2000 figures.

 

Based on an average household size of 2.3 people for residential customers, as well as 15.2 people for multi-family customer, the population has increased 8,824 people since 2000, according to water utility records (Table 4). The average household size figure of 2.3 people is from the Census 2000, while the 15.2 people for the multi-family category is derived as a proportion of water usage compared to number of accounts.

 

 

 

If the population increased 8,824 people from 2000 to 2005, then that would put the January 1st, 2006 population for the city at 88,922 people according to water utility records (Table 5). That represents a less than 1% change over estimates produced using the building permit method.

 

 

It is also important to note, that if the Census Bureau estimates for 2005 were correct, then the residential water accounts added would amount to an average household size of .47 people.

 

III. Other Communities:

 

Eight (8) communities have already successfully challenged 2005 Census population estimates since they were released in late June of 2006.  Thirty-eight (38) cities and counties successfully challenged 2004 Census population estimates, including Blue Springs, MO and Great Bend, KS. Twenty-seven (27) cities and counties successfully challenged 2003 Census population estimates, including Manhattan, KS and Ottawa, KS.

 

St. Louis, MO has successfully challenged the Census estimates for the last three years based on building permit records. Other cities, like Millington, TN are preparing challenges because of the fact that it is estimated that the state share of revenue with cities amounts to $110 per resident, and is based on Census population figures.

 

Utah County, Utah, whose main city is Provo, is in the process of appealing their Census estimate and has noted that for areas where there is a high student population, the Census Bureau’s methodology of using federal tax data is flawed because students might not file with their school address. Utah County currently uses a system that uses data from school enrollments and utility hookups to estimate its county population.

 

In the District of Columbia, they used a combination of housing and utility data to challenge the recently released July 2005 population estimate and were successful.

 

IV. Recommendation:

 

Staff recommends that the City challenge the Douglas County and City of Lawrence U.S. Census Bureau estimates.