IPFNA_Growth Analysis Memo_Jan_06

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Average Household Size When calculating an impact fee, data on average house hold size for various types of housing units is a critical component. The most recent and reliable data on averag i County is the 2000 U.S. Census. As shown in Table 3 belo w, average household size varies by housing type, ranging from 1.99 persons per mobile home unit to 2.87 persons per single-family detached unit. Table 3 AVERAGE HOUSEHOLD SIZE BY HOUSING TYPE Household Occupied Avg. Housing Type Population Units HH Size Single-Family Detached123,43142,9842.87 Multi-Family21,9049,7042.26 Mobile home5912971.99 All Housing Types145,92652,9852.75 Source: 2000 U.S. Census for the County of Hawai i, Summary File 3 (sample data). For single-family units, the County may desire to vary the fees the only measure of dwelling unit size recorded by the Census Bureau is bedrooms and total rooms in the dwelling unit, it is recommended that the fees be based on square footage rather than number of bedrooms or rooms in a unit. Although some municipalities charge impact fees on the basis of bedrooms, it can be an administrative challenge to determine the number of bedrooms when there is a financial incentive to disguise bedrooms as someth ing else (a den or storage room, for example). An alternative is to translate bedrooms or total rooms into size ca To determine a relationship between the unit square Figure 3 footage, bedrooms and household population in Hawai i RESIDENTS BY UNIT SIZE County, the consultant compiled data on all 630 single- family homes listed for sale in the County from the National Association of Realtors website (www.realtor.com) on October 19, 2005. These on-line listings give square footage and the number of bedrooms for each home offered for sale. A variable for average household size was added, consisting of the average household size multipliers by housing type and number of bedrooms derived from 2000 U.S. Census sample data. Regression analysis was then performed to determine the relationship between unit size in square feet and persons residing in the unit. Both linear and logarithmic regressions were performed. The linear regression was statistically significant, with the linear 1 equation accounting for 35 percent of the variation. 1 The linear equation for single-family units is y = 0.000223 * x + 2.6732 (r-square = 0.354597), where x is square feet of living area and y is household size. H C \I N A ÐG A M January 5, 2006, Page 4 AWAI I OUNTY NFRASTRUCTURE EEDS SSESSMENT ROWTH NALYSIS EMORANDUM