Living in downtown Wichita

Wichita economic development officials use a circuitous method of estimating the population of downtown Wichita, producing a number much higher than Census Bureau estimates.

Recently the Wichita Business Journal reported:

Getting more people to live in the core was clearly one of the most important tasks for the city. Back in 2010, the report said downtown Wichita was ripe for an additional 1,000 housing units.

That goal seems to have been met. According to a recent report from the group Downtown Wichita, 835 residential units have been completed since 2010. An additional 742 units are in development downtown, where about 2,100 people live today. ¹

The report referred to is the 2017 State of Downtown Report. ² While this report highlights the number of people living in downtown Wichita, it no longer reports the number of people working in downtown. ³

How does Downtown Wichita arrive at the number of residents in downtown? An endnote from the report gives the details:

The 2010 U.S. Census states the population in the 67202 area code is 1,393. Per Downtown Wichita records, 702 units rental units have opened in the Downtown SSMID district since 2010 when the Census was taken. Per data provided directly from the Downtown residential rental properties, the absorption rates of the market rate units has an average of 85%. Per the U.S. Census Bureau, 2011-2015 American Community Survey 5-Year Estimates, the average size of renter-occupied units is 1.25 persons. Therefore, an estimate for the current population is 2,138. ⁴

What DW has done is to take a reliable figure (the 2010 decennial census) and extrapolate forward to 2016. (Presumably 2016, as the report doesn’t say.)

But there are a few issues, as follows:

First, the calculation includes 702 rental units that have opened since 2010. Have any rental units closed since then? That would be good to know. Curious is that the report prominently mentions “835 units completed since 2010.” There have been condominiums that have opened since 2010. Why would DW use only rental units in its calculation?

Second, the DW calculation makes use of two estimates, absorption rate ⁵ and size of renter-occupied units. (What about size of owner-occupied units?) Each of these is an estimate that has its own error probabilities, and those errors compound when multiplied.

Third, there is no need to go through this roundabout calculation, as the Census Bureau has provided an estimate for the population of downtown in 2015. Data from the American Community Survey ⁶ estimates that the population in downtown Wichita for 2015 was 1,438, with a 90 percent confidence interval of plus or minus 242. ⁷ This means the Census Bureau is confident the population of downtown Wichita in 2015 was in the range of 1,196 to 1,680, that confidence factor being 90 percent.

But DW says the population of downtown is 2,138, which is far — really far — outside the range the Census Bureau gives for the 2015 population. While DW’s population estimate is probably for 2016, it still lies far outside the range of probability, based on Census Bureau estimates.

It’s really curious that DW doesn’t use the Census Bureau estimate of population. That population estimate comes directly from the Bureau’s American Community Survey 5-Year Estimates for 2011 to 2015. DW didn’t use that number, but it relied on the same body of data to get “average size of renter-occupied units” for 2015.

Why would DW use the Census Bureau for one datum but not another, especially when the Census Bureau data reports the statistic DW is trying on its own to estimate in a roundabout manner?

It’s simple. DW’s calculations produce 2,138 people living in downtown. The Census Bureau estimate is a much smaller number: 1,438.

By the way, DW’s calculations start with the 2010 Census Bureau population for downtown. Of the downtown population of 1,393 that year, 253 were men living in institutions like the Kansas Department of Corrections Wichita Work Release facility at Emporia and Waterman Streets. It has a capacity of 250. ⁸

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Notes