PROJECTIONS

It is expected that with continued development pressures spreading eastward across Lake County, Perry Township will continue to grow both in terms of population and housing units. Increases in population and housing are heavily dependent on a number of factors, many of which are beyond the control of the Township, such as regional and national social, economic, housing, and technological trends. It is valuable, however, for planning purposes to make projections of population and housing change based upon reasonable assumptions regarding those factors or trends which are beyond the Township's direct control.

The following is a set of three population projections based on different models and assumptions. As indicated in the table, the three twenty-year projections of Township population, although projected using different methods, differ by a little more then 500 persons or about 5%. The similarity of the projections provides some comfort level for planning based upon the projections. Both projections "A" and "B" use historical trends as the basis for projecting future growth. Projection "C" is based on the assumption that there will be an increase in demand for residential development within Perry Township.

*Denotes years with projected population

PROJECTION METHODS

Projection "A"

This projection is based on historic population growth factors and trends. Population growth within any community results from the combination of birth rate, death rate, in migration, and out migration. It is possible to develop projects for future population by looking at historical trends in each of these four factors. A simplified method of this approach is to use historical population change data to identify the combined effect of those four factors rather than calculating each factor separately. The resulting rate of change is then applied to the 2000 population obtained from the 2000 U.S. Census to calculate 2010 and 2020 populations.


Projection "B"

This projection is based upon the relationship between housing and population and uses housing statistics to project population change. Three factors are critical to this projection technique. First is the number of new dwelling units constructed annually. This number is projected based upon historic building permit data. The second factor is the vacancy rate for dwelling unit. It is necessary to project anticipated changes in the percentage of vacant housing units. The third factor is the number of persons per household. This factor is applied to the projected number of occupied housing units to obtain a projection of population. Historically within the United States, average household size has declining. It is anticipated that that trend will continue for the foreseeable future. A projected average household size of 2.75 persons per househould was used or purposes of these projections. That is less than the current aveage of 2.88 persons per household as noted in the Housing Chapter because it is anticipated that over time the average household size within Perry Township will tend to gravitate closer to the Lake County average of 2.50 persons per household. The change in average household size was projected by taking the average decrease in household size from 1980-1990 and 1990-2000, and applying that for 2010 and 2020.


Projection "C"

Perry Township has the potential for an increase in the rate of growth in the future which is not represented by historical trends. For the purpose of this projection, the increased growth will be represented by a fairly conservative 2% increase in the average annual building permits each year. This demand for housing is evident by the low 1% vacancy rate on owner-occupied units. This projection again uses a projected average household size of 2.75.