Memorandum
City of Lawrence
Planning Department
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TO: |
Dave Corliss, City Manager |
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FROM: |
Planning Staff |
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CC: |
Scott McCullough, Director of Planning and Development Services Sheila Stogsdill, Assistant Planning Director |
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Date: |
September 4, 2007 |
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RE: |
Population Estimates and LUCA Update |
I. Introduction
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.
During this time, staff felt that the population estimates that were released for July 1, 2005 for both the City of Lawrence and Douglas County were low. Both the City of Lawrence and Douglas County estimates were successfully challenged. As a result, staff has been producing biannual population estimates using the Census Bureau’s methods.
In addition to the above, this memo will address the process and participation requirements regarding the Local Update of Census Addresses (LUCA) program for the upcoming Decennial Census in 2010.
Recommendation: Staff has determined, with confidence that the US Census Bureau is underestimating both the City of Lawrence and Douglas County population estimates for July 1, 2006. Because we have access to the best available data in our building permit records, and since these figures are used to compute per capita information and to appropriate funding, staff recommends that we once again challenge the City and County population estimates.
II. Population Estimates and Challenge
a. Introduction
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.
b. Previous Methodology
Last year, staff investigated the methodology that was being used by both staff and the Census Bureau and found that both methods were similar. As a result of filing the challenge last year, staff decided to make a few small changes to the methodology so that it would be the same as the Census Bureau’s challenge methodology. 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. Federal agencies provide tax records, Medicare records and some vital statistics information, while state 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 which uses housing unit change to distribute county population to sub-county areas. The Census Bureau’s method for challenging those estimates is slightly different in that it does not distribute the county population to the sub-county level in a top-down fashion, but rather calculated population based on housing unit change at the sub-county level. The formula that was used last year reads as follows:
(HU – DU) *.98 * PPH * OCR + GQ = Population Estimate
HU = Housing Units Added
DU = Demolished Units
.98 = Assumes that 2% of all units building permits applied for are never built
PPH = Persons per household
OCR = Occupancy rate
GQ = Group Quarters Population
With each new issue of July 1st estimates, the population estimates program revises estimates for years back to the last census. Previously released estimates are superseded, and our successful challenge of both the City and County’s July 1, 2005 population estimate is reflected in the July 1, 2006 estimates that were recently released. The following table details the population estimates using the Census method that staff has produced in the last year.
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Table 1: Summary of Population Estimates using the Census Method |
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Date |
Population |
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July 1, 2005 |
88,664 |
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July 1, 2006 |
89,690 |
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January 1, 2007 |
90,475 |
c. Revised Methodology
After the Census Bureau released the population estimate of 88,605 people for July 1, 2006, staff requested a challenge packet that details the methodology used in determining that figure. Staff discovered that the Bureau changed their methodology slightly by using separate occupancy and persons per household figures for multiple family and single family. The new formula would read:
[(SHU – SDU) *.98 * SPPH * SOCR] +
[(MHU – MDU) *.98 * MPPH * MOCR] + GQ = Population Estimate
SHU = Single Family Housing Units Added
SDU = Single Family Demolished Units
MHU = Multi Family Housing Units Added
MDU = Multi Family Demolished Units
.98 = Assumes that 2% of all units building permits applied for are never built
SPPH = Single Family Persons per household
SOCR = Single Family Occupancy rate
MPPH = Multi Family Persons per household
MOCR = Multi Family Occupancy rate
GQ = Group Quarters Population
As a result of this new change, staff revised its previous July 1, 2006 estimate, as well as the January 1, 2007 estimate using the new methodology.
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Table 2: Summary of Population Estimates using the revised Census Method |
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Date |
Population |
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July 1, 2006 |
89,127 |
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January 1, 2007 |
90,064 |
This represents a difference of 522 people when comparing the new methodology figure to the Census Bureau estimate. Staff has concerns over this change in methodology, specifically with respect to the multi-family persons per household and occupancy rates. It is unclear where these figures were derived from, and in a college town such as Lawrence, these figures may not be accurate. Staff is conducting ongoing research on this issue, but it may not be until the 2010 Decennial Census that we know if those figures are correct. In the meantime, staff will use the new methodology in computing population estimates.
d. Participants
Staff has the understanding that Lawrence’s population estimate, and the estimates of the other communities in Douglas County, are shares of the Douglas County estimate. In other words, all of the population estimates of the communities and unincorporated areas of Douglas County must equal the population estimate for Douglas County. An approved challenge that only raises the Lawrence population will not raise the Douglas County population. Rather, it will likely lower the population estimates of the other communities in Douglas County in order to fit the new Lawrence population estimate into the overall Douglas County estimate.
Therefore, staff feels the best course of action will be to challenge the population estimate of Douglas County, as well as the population estimate for the City of Lawrence. This means we will need to include the County Commission in the challenge process as well. If the City authorizes the challenge process, staff will also seek authorization from the County Commission and will also contact other incorporated cities of Douglas County to inform them of our decision to challenge.
e. Time Commitment
Staff computes population estimates for the City on a biannual basis and therefore staff already has completed all of the necessary research to challenge the 2006 population estimates. We are currently in the process of gathering the necessary data from the County and working with the other communities for those aspects of the challenge. That effort will not require a large amount of additional staff time. .
Staff has the US Census Challenge packet in hand. Completing that packet will not require much time because, again, we have already completed the data intensive work. All necessary approvals and paperwork would need to be completed by the October 1st, 2007 challenge deadline.
III. Local Update of Census Addresses (LUCA) Program
The Local Update of Census Addresses program (LUCA) allows local governments to review and comment on the list of housing unit and group quarters addresses that the Census Bureau uses in developing its Master Address File (MAF) for the 2010 Census. The City of Lawrence participated in this program in for the 2000 Census and is again being asked to participate for the 2010 Census. Staff has already attended an introductory meeting and is scheduled to attend training sessions at the beginning of October 2007. It is important that the City participates in this program in order to provide the best possible data to the Census Bureau so that the 2010 Census reflects accurate data.