Memorandum

City of Lawrence

Planning Department

TO:	Dave Corliss, City Manager Debbie Van Saun, Assistant City Manager
FROM:	Planning Staff
CC:	Sheila Stogsdill, Acting Planning Director
Date:	2/23/07
RE:	Population Estimates

Summary

Staff has recently reviewed and updated population estimates for the City of Lawrence. Traditionally, the City has used a method that utilizes building permit data, demolition data, average household size, and vacancy rates. This method adds housing units created starting with January 2000 to the 2000 Census figure.  Using this method, the population estimate for January 1, 2007 is 90,335 people.

Staff also investigated the use of the method that the Census Bureau uses in its population estimates. This method also uses building permit data, demolition data, average household size, and vacancy rates. This method differs in that it assumes that 2% of all units that a building permit was granted for never get built. In addition, the time periods for adding housing units are shifted slightly. The model assumes that it will take an average of 10 months to build a multi-family structure, and an average of 7 months to build a single-family structure once a building permit is pulled. Therefore this method adds building permit data from 1999 to the April 1, 2000 census figure; because it assumes that there is a gap between when a permit is pulled and when a structure is occupied. Using this method, the population estimate for January 1, 2007 is 90,475 people.

The difference between the Traditional method and the Census method is due to the difference in time from pulling a building permit to final occupancy, and the assumption that 2% of all housing units for which a building permit is applied for are never built. That difference is 140 people for January 1, 2007 or less than .2%.

Conclusion

In staff’s opinion, the Census method is the best practice for estimating population because of the built in time-lag, the assumption that 2% of all building permits are never built, and because it is consistent with Census Bureau methodology. Therefore, staff has concluded that the City should use the Census Method for population estimates, but it would be beneficial to keep updating the traditional method of population estimates in order to maintain historical trend data. In addition, staff will complete the population estimates for the City using the Census method on a bi-annual basis (January 1^st and July 1^st) in order to keep consistent with our local government calendar year and be able to compare data with the annual release of the Census Bureau estimates on July 1^st.