The demography of the West is changing dramatically along many dimensions. We have picked eight of these changes to discuss because of their relevance for wildlife and natural resource management. These eight are:
You might have seen the map that is updated after every new decennial census that shows the exact location of the mean population center of the United States. That center of gravity has moved steadily westward for over 200 years, and also southward since about 1970. In 1790 the first census determined that the center was in eastern Maryland, and over the next 20 decades it moved across Maryland, through Virginia and West Virginia, jumping trough Ohio and Indiana, and continuing on through Illinois and into Missouri. In 2000 the U.S. population center was in Phelps County, Missouri, a modest-sized county of about 40,000. Surrounding Phelps County is a broad swath of counties that extends from Kansas to North Dakota that are stagnant or losing population, yet the center of population for the U.S. is continuing its westward march by leaps and bounds through this low-density low-growth Midwestern heartland. What is dragging this center of gravity westward is the high population growth in the Pacific and Rocky Mountain states.
For most of this history of the westward movement of the U.S. population, the migration of people from east to west was indeed the driving force. From the mid-18 th century until the mid-19 th century the migration was more like a bleeding of population from the densely populated eastern core cities into adjacent territory to the west. After 1850 larger numbers of people moved in successive waves starting with miners and homesteaders, followed by thousands of European immigrants and the native born U.S. citizens they were displacing. New communities suddenly sprouted up throughout the West as the railroad connected the coasts. Finally there followed the great California migration during the post- WW II period, extending through the 1970's.
Since 1850, the West has gained in the share of the total U.S. population in each and every decade, and higher than average growth is projected to continue for the foreseeable future (Figure 1).In 1980 the West surpassed the Northeast in population share, and in 2002 it surpassed the Midwest. Throughout most of the post- WW II period western growth was stimulated by domestic migration of young adults to California, and by the high natural increase (excess of births over deaths) that characterizes California's youthful age structure. In the 1980's and 1990's however, as domestic migration to California turned negative, international migrants from Latin America and Asia picked up the slack.
During the 1990's, the West was still the fastest growing region of the country (Figure 2), and during both the last decade of the 20 th century and the first years of the 21 st, the West's eight-state Mountain Division (MT-ID-WY-CO-NM-AZ-UT-NV) led the nation in percent growth (Figure 3). But population growth in the West no longer depends on migrants from the East. As we shall soon see in some detail, international immigration and high natural increase has made the West its own engine of growth. California's high growth from international migration and natural increase alone has created the situation where the rest of the West has become a safety valve for relieving mounting population pressure in California. This growth dynamic is likely to be sustained for the next several decades.
For most states in the Mountain West, recent population increases have taken place across all age cohorts, signaling the fact that net migration continues to be a significant factor in population growth (Figure 4). When the three components of population growth are measured separately, we see that the rate of growth from net domestic migration in the Mountain Division is by far the largest in the country (Figure 5). Natural increase in the Mountain Division is also high, rivaled only by that in the five-state Pacific Division (CA-WA-OR-AK-HI). The combination of high growth from both natural increase and from international migration in the Pacific Division, and especially in California, guarantees that the growing net domestic migration losses from California we have observed since the mid-1980's will be sustained in the future (Figure 6). Most of this net out-migration from California is flowing into the adjacent states of Arizona, Nevada and Oregon. But California migrants also move directly to other western states in significant numbers, and in turn create ripple effects throughout the region.
Historical estimates that separate out international and domestic migration are time limited (nothing available at the county level before 1990) and somewhat unreliable. International migration estimates rely on Immigration and Naturalization Service (INS) data that under-reports illegal immigration, and domestic migration estimates rely on Internal Revenue Service (IRS) estimates that miss about 20 percent of households nationwide. Combining international and domestic migration into one total net migration value, and estimating this value as a residual of population growth minus natural increase, can give a better estimate of overall net migration and covers a longer time period. Population estimates for states and counties going back to 1970 are robust and are based on a slew of administrative data such as school enrollments, driver's licenses, Medicare enrollment, and other such data. Likewise, birth and death records are fairly accurate back to 1980. Figure 7 shows that California's present levels of population growth are high, even by historic standards. Only in the late 1980's, before net domestic out migration from the Golden State began to reduce the impact of high foreign immigration, was total growth higher.
Since California has some of the highest housing values in the U.S., high home equity accumulation and large numbers of retiring workers with generous pensions (policeman, fireman, teachers, military personnel, other government employees, etc.) have created a situation where it is possible, indeed desirable, for retirees to relocate out of state. A popular choice has been other western states with lower housing costs, lower taxes, greater recreational opportunities, and a slower pace of life. Many of these "retirees" are still in their 50's, and many re-enter the labor force in their new locations. We can conservatively expect California to annually give up between 100,000 and 200,000 net domestic migrants to other states as the baby boom generation begins to retire.
Other domestic out-migrants from California typically include younger adults who are looking for a fresh start in another state with lower costs of living, or those who have family ties in other states and who choose to relocate there when they start their families .There are also increasingly more self-employed young adults who can work from any location and are making their residential choices based on quality of life considerations that take them to states like Colorado, Oregon or Montana.
The reciprocal relationship between population growth in California and growth in other states in the West can be seen by comparing Montana's growth charted in Figure 8 with California's in Figure 7. The high Montana growth from net migration in the early 1990's clearly mirrored California's losses during the same period .This demographic relationship is replicated for other states and counties in the West.
I have focused most or my attention in this chapter to documenting and understanding the trends and differences in raw population growth. But one trend that we should keep firmly in mind is that population in the West is spilling all over the countryside. In Montana, the rate of growth of unincorporated places during the 1990's was more than twice the rate of incorporated places (Figure 9). Furthermore, households are increasing faster than population (Figure 10), and most of the increase in households is evermore automobile dependent (Figure 11). Population growth is what we can readily measure in the demographic statistics. But it is the appearance of businesses and houses where before there were none, and the ever-increasing number of roads, cars, trucks and traffic—at rates of growth even faster than population—that we are all experiencing that defines sprawl. Even places with stagnant population growth in the West and in many other parts of the country have been sprawling.
Figure 8 showed how highly variable population growth in Montana has been over time, and that the variability is due primarily to fluctuations in net migration. It also shows that natural increase has been gradually declining (fewer births and more deaths because of population aging) and that this component of growth is becoming less and less of a factor. What Figure 8 does not show is that population growth across the state is also highly uneven. In fact, the growth trend in Figure 8 is made up of the average of growth that is much higher in the western part of the state, negative growth in the eastern part, and modest positive growth in the central counties at levels that are well below the state average (Figures 12, 13, 14). Instead of charting growth trends in one state of Montana as represented in Figure 8, we should really be thinking of three states of Montana as represented in Figures 15, 16, 17. Western mountain counties have experienced high sustained growth on average in recent years, and many western counties including Flathead, Ravalli and Gallatin Counties, have what can be considered extremely high growth rates. Central Montana front-range counties have oscillated between positive and negative growth, and now appear to be in a slightly negative growth phase. Eastern plains counties have had sustained negative growth for the past two decades.
Overall, (Figure 18) the 21 western mountain counties contained 57 percent of the state's population in 2000, up from 51 percent in 1980. The 14 central front-range counties contained 31 percent of the state's population, slightly less than the 33 percent it contained in 1980. The 21 eastern plains counties held 12 percent of the state's total population, down from 16 percent in 1980 .There is every reason to think that these trends in the three parts of Montana will continue well into the future.
Much attention is given to raw population growth and to net migration when defining important demographic trends in the West. Net migration is just what it says - "net." It is the sum of larger gross flows of people into and out of an area in a given time period. These large gross flows represent a churning of the population that has important consequences for much of civic society —f rom public education to labor force activity and consumer behavior to recreation to voting patterns to criminal justice to volunteer participation. For the entire state of Montana, 24 percent of the population enumerated in the 2000 census lived in another county in 1995. For high in-migration counties like Ravalli County, that figure was 31 percent, and for young adults the figure exceeds 40 percent. Even in low growth counties in eastern Montana, population churning is significant (Figure 19). A good example of the importance of population turnover can be found in Yellowstone County. Here, there was only a net gain of 258 people over the age of 5 in 2000 who were living in a different county in 1995. But this small net gain resulted from 23,665 people moving into Yellowstone County, and 23,407 people moving out of the county during the same five-year period. These gross domestic in-migrants from 1995-2000 represent 18 percent of the residents of Yellowstone County in 2000.
During the late 1990's, population growth in Ravalli County was high because net in-migration was high (Figure 20). Population turnover was even higher during this period (Figure 21). During the late 1980's when Ravalli County's net migration and population growth was much lower (Figure 22), the 1990 census counted only about 525 more people who moved into Ravalli County between 1985 and 1990 than moved out. But this net number was the result of over 6,400 people moving in between 1985 and 1990 (and still resident in the county for the 1990 census), and about 5,900 moving out (Figure 23). These gross in migrants the previous five years represented 26 percent of Ravalli County's 1990 population. In 2000 residents who were recent domestic in-migrants represented about 31 percent of the total 2000 population.
Typically, most in-migrants in any particular county come from other counties in the state, and most out-migrants go to other counties in the state. In high growth counties, a higher proportion of in-migrants come from out of state compared to low in migration counties. In Ravalli County, for example, 32 percent of the approximately 10,300 in-migrants over the age of 5 who arrived in the late 1990's came from other counties in Montana. About 35 percent of the out-migrants moved to other counties in Montana. The next most popular origin states for in-migrants were California and Washington, with 15 and 11 percent respectively. Below these top three in-migration origin states are many others with low shares, typically under one percent each of total in-migrants (Table 1). On the out-migration side, this pattern is replicated (except that Washington is the second choice followed by California). The Ravalli County gross-migration pattern is typical of other high growth counties in western Montana. In eastern Montana a higher proportion of in and out-migrants come from and go to other Montana counties, and the list of states serving as origins or destinations is shorter.
Population churning could be even more significant if the in-migrants are not only different people but have different social characteristics than the out-migrants. Analyses of the limited data available on characteristics of migrants show that, for the most part, these differences are usually not extremely large. We can illustrate this by comparing in Figure 24 the ages of in and out-migrants to Ravalli County from the 1990 census (2000 census data on characteristics of migrants were not yet available at the time this chapter was drafted). Out-migrants are only slightly younger and in-migrants slightly older, with an out-migrant advantage in the late teens and early 20's and an in-migrant advantage in the age range 55-64.
One reason why the characteristics of in- and out-migrants are generally broadly similar is that in-migrants in one period are often the very out-migrants a few years later. Not all migrants intend to set down permanent roots, and even for those who intend to do so, they are not always successful. On average, it appears that people in the Rocky Mountain West are more mobile than people in other parts of the country.
Still, population churning is important for the demography of the West because new people bring new ideas, resources and expectations. In-migrants must become educated about the politics and priorities of the places they have chosen to live. Out-migration means a loss of human capital in terms of specific knowledge and a sense of place. Civic activities that depend on citizen volunteers are less predictable in places with high population turnover.
All of the data presented thus far pertain to the resident population. Non-residents, including second homeowners, snowbirds who might have once been residents but now spend more than 6 months of the year in another state, visitors, and tourists are not counted in the census or in any other demographic data bases. They are like an iceberg - they can have a huge impact on a community but they lie mostly below the data line. They are, however, increasingly responsible for the economies and infrastructure growth being experienced by counties throughout the Rocky Mountain West.
As we look forward a decade or two into the future one demographic trend is certain. Barring some dramatic increase in mortality, the population present today will age. We can visualize the aging of Montana's population by comparing population pyramids for 1980, 1990 and 2000 (Figure 25). A horizontal bar has been placed at age 55. In 1980, the Baby Boom generation was in its late teens through early 30's, with the largest of its cohort in the mid-20's. Ten years later, in 1990, the bulge in the population pyramid was at age 35, and in 2000 it was at age 45. As it passed through these age groups, the Baby Boomers became parents themselves, and the Echo Boom generation appeared at the bottom of the age pyramid. Echo Boomers were between ages 5 and 25 in 2000, and will themselves become parents over the next two decades adding another bulge at the bottom of the population pyramid.
While it is difficult to project the exact size of future cohorts of young adults and their children living in Montana because of the uncertainty about future levels of net migration and fertility, it is a straightforward proposition to project the aging of older adults. In Figure 26 a highly simplified projection is charted, based on the assumptions that there is zero net migration and zero fertility, and that men and women have the same future life expectancy (using the 1995 Montana life table). Accurate assumptions about net migration and gender differences in life expectancy will change the details of the projection, but not the story that is presented in the figure. (Note that the 85+ age group in Figure 25 has been expanded to single years of age past 100 in Figure 26). In 2010 the Baby Boomers will sit right astride age 55, with approximately half being older and half being younger. By 2020, the mid-point of the Baby Boomer age group will be 65, again with half the generation being older and half younger. A similar exercise carried out for virtually any level of geography in the Rocky Mountain West, or indeed most areas in the country, will yield similar results.
Recognizing the effects that net migration will have on the Baby Boomer generation resident in Montana and in other areas of the West, it is likely that the size of the bulge will be larger than in Figure 26. It is also true that population churning will mean that a high proportion of surviving Baby Boomers in 2020, perhaps as many as half, will be different persons than those resident in Montana in 2000.
 These omitted areas include trends in marital status, changes in household and family composition, changes in racial and ethnic makeup, trends in educational attainment, and trends in labor force participation of adults.
This report was completed in 2004.