Memorandum

City of Lawrence

Planning and Development Services Department

TO:	Dave Corliss, City Manager
FROM:	Planning Staff
CC:	Scott McCullough, Director of Planning and Development Services Sheila Stogsdill, Assistant Planning Director
Date:	December 24, 2007
RE:	Population Projections Update

Staff has been asked to determine what effect, if any, the recent growth trends will have on future population projections. This memo serves to provide a response to that question, as well as an update on efforts to effectively estimate and project population growth.

Background

Planning staff undertook an effort during the summer of 2006 to determine if the Department had been using best practice methods of projecting future population for Lawrence and Douglas County and estimating yearly population for Lawrence.  Staff researched other community’s practices, as well as researched the Census Bureau’s methodology, and concluded that we use the best practices available for determining population estimates and projections. At that time, staff determined through comprehensive testing methods that the medium-range population projections in Horizon 2020 were on target.

Analysis

Population projection methods primarily rely on trend data, and therefore are only officially undertaken every decade after the Census Bureau releases the Decennial Census Data. Staff will therefore officially release population projections after the 2010 Census numbers are calculated.

In the meantime, staff has investigated the impact that the recent slowing of population growth might have on future population projections. In order to do this, staff had to make the assumption that the recent (i.e. last few years) slowdown of growth would continue indefinitely.  Generally it is difficult to make assumptions on future population growth based on trends from a small period in time and typically would not be considered statistically correct.   

Using the population estimate figures from the Census Bureau since 2000, Lawrence has grown an average of 1.66% a year. However, since 2005, the average annual change amounts to a less than 1% growth rate.

Staff analyzed the effects that different average annual growth rates would have on the 2010, 2020 and 2030 population projections, as well as utilized a simple linear regression projection model using 2000-2007 data. The data shows that using average trends from 2000-2007; projections are still in line with the medium projections listed in Horizon 2020. Using more recent trends, from 2005-2007 (1% average annual growth rate), population is projected to be slightly above the low projections listed in Horizon 2020.

Outcome

The information found in Table 3 is based on trend data for only a few years.  Staff is cautious of the conclusions that can be drawn from Table 3 because it is based on limited data.  Staff will continue to monitor the growth patterns in the city by issuing biannual population estimates and making decennial population projections at the appropriate times.