Population growth projections in the study region are based on results that were pertinent in the 1980´s. These growth projections are incorporated into the Metropolitan Washington Council of Governments (MWCOG) that are the basis for all the modeling that has been done in the WTC study area since 1990. The MWCOG data was originally developed in 1990 as "Round 5.0." Although some adjustment to the growth has been made, it still reflects the unusually high rate of growth that began in the early 1980´s and increased steadily until 1988. These projections do not accurately reflect actual trends either past or present. They tend to be simplistic extrapolations of the population, rather than using the underlying fundamental effects reflected in the annual growth rates. For example the population growth in PWC was about 10% per year in 1970, but fell dramatically and was only about 3% per year in 1978. In 1980 it began a second rise, partly as a result of the rapid growth in the Federal Government, but also as a result of the "Baby Boom," and peaked in 1988 at 5%-6%. Between 1989 and 1996 it declined rapidly to an estimated value of 2.4% per year. The MWCOG projection is a straight line that computes as 2.7% per year through the year 2020, resulting in a population of 428,000. As demonstrated below this is a gross over-estimate.
The attached Figure 1 provides data1 and an analysis of the population in PWC. It demonstrates in graphic terms the dramatic reduction in the rate of growth that began in 1988. The best estimate of the rate of growth in PWC for 1997 is less than 2% per year. For all of Northern Virginia the present estimated growth rate is less than 1.2% per year. For all of Virginia the estimated growth rate is less than 0.9% per year, and for the US as a whole the present growth rate is less than 0.9% per year. All of these rates are decreasing with time. For example the Weldon Cooper Center in a recent publication 2 documents that for Virginia the rate of growth has declined from 1.6% per year in 1991 to 0.9 % per year in 1996. Data for Virginia from 1970 to the present are shown on Figure 1.
It is expected that the rate of growth for PWC as well as Virginia as a whole will be significantly lower in 2000 than it is now. The US Census Bureau points out that these are true secular trends and that there is no basis for not assuming that they will continue because they are based on some very fundamental changes that are occurring. Primarily the number of births is declining because women are having fewer children. For the United States the birthrate has declined to about 1.9 children per woman. Secondly, as the population ages, the death rate increases. Finally, contrary to the common belief, migration has declined steadily for the past decade and as new laws go into effect, population increases from this source will continue to decline.
For the years beyond 2000, the population projections used by MWCOG are increasingly overstated. In both the Disney´s America Transportation Analysis and the WTC MIS Traffic Analysis 3 the projected rate of growth for PWC is 2.7% per year. If the PWC population growth rate stabilizes at 1.8% per year after 2000, the 2020 population projection would be about 370,000. If the growth continues to decline and is 1% by the year 2020, the population would be less than 330,000. Smaller growth rates cannot be ruled out, but growth rates as large as 2% are unlikely and are difficult to justify. Obviously these reduced population projections will reflect a reduction in the forecast traffic volumes. Table 1 provides some comparisons of population figures for MWCOG rates and for rates that are derived from the actual census data along with estimates provided by Prince William county. MWCOG projects that the 1996 population of 257,000 would increase by an addition 171,000 in the 14 years from 1996 to 2020, an increase of 67%. A realistic growth based on the established trends is 28%, increasing the 1996 population by 71,000. MWCOG´s projection is nearly two and one half times larger than a reasonable projection, and is more than twice as large as can be justified by the largest imaginable projection of the growth rate.
For the rates that appear to be the inevitable consequence of the trends shown in Figure 1, growth rates approaching 1% per year are likely after the year 2000. Similar trends are present for all parts of the region although actual rates will differ, and the inevitable decline in growth to the low values may be delayed by a few years in some areas as the birth rate trends overcome other factors.
| Population In 1996 | Population In 2020 | % Increase | |
| MWCOG Prediction | 257,600 | 171,000 | 66% |
| Realistic Forecast | 257,600 | 70,300 | 27% |
| MWCOG´S OVERESTIMATE ABOVE THE REALISTIC FORECAST | 100,700 | 144% |
MWCOG plans on the basis that 100,000 more people will live in Prince William County than will be the case. Considering that today the total population is only 257,600, this is a huge overestimate; a phantom population increase that is unbelievable. A correspondingly huge additional demand for travel on roads that are not actually going to be required is a second major consequence of MWCOG´s overestimate.
The very large excess growth projected by MWCOG cannot be justified by any reasonable way of looking at the growth rates shown in Figure 1. And these data are the direct result of the actual census data and the annual estimates made by Prince William County. These greatly exaggerated MWCOG population figures have the immediate consequence of leading to the justification of the construction of major new road facilities such as the Western Transportation Corridor.
The traffic projections in both the Disney´s America Transportation Analysis and the WTC are arguably overstated for their target years as demonstrated by the results shown above. Traffic forecasts for 2020 should be reduced proportionally to the change in population growth from 66% to 27%.
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1. Population data was provided by Mr. William Vaughn of the Prince William County Mapping Staff.
2. Martin, Julia H., 1996 Virginia Population Estimates, Spotlight on Virginia, Vol. 1, No. 1 February 1997
3. All of the recent traffic analyses carried out for Northern Virginia and particularly the Metropolitan Washington area have used these population projections that were developed during the height of the "Baby Boom". For Prince William County, the growth rate is projected to be 2.7% per year through the year 2020. The recent Washington Board of Trade study uses this figure, as will the I-66 MIS and presumably any study involving the US 29 corridor.