In 1950, Colorado's population was just over 1.3 million. By 1980, numbers were approaching 3 million. During the 1990s, the state added over one million inhabitants, or about 275 people each day. In 2000, Colorado had ballooned to 4.3 million residents. Thus, over the past 50 years, Colorado's population has more than tripled in size. In the past ten years alone, it has grown by almost one-third. There are now more people living along the Front Range than there were living in the entire state ten years ago.
 
What accounts for this growth? Populations grow or shrink as a result of shifts in three demographic variables: fertility, migration, and mortality. Changes in population size are dependent on net migration (people moving into the state minus people moving out of the state) and natural factors (births minus deaths). Between April 1, 1990 and July 1, 1999, natural increase in Colorado accounted for net growth of 288,209. During the same period, the Census Bureau estimates net domestic migration for Colorado at 402,832 and net international migration at 65,380. Thus, natural increase accounted for 38 percent of all growth during that period, over half came from migration from other states, and the remainder was due to migration from other countries.
 
In the 1990s, Colorado was home to five of the nation's ten fastest growing counties. Douglas County, the fastest growing county in the nation, almost tripled, growing from 60,000 to 176,000. Elbert County was third with a 105 percent growth rate and says it fears its population explosion will soon overwhelm the area's law enforcement, roads and bridges, and social services. Park, Custer, and Archuleta were also in the top ten.
 
In Summit, the sixth fastest growing county in the state, county commissioner Bill Wallace says the population growth means "we have more traffic lights and more asphalt. A lot more people commute for work. Lots that were vacant are no longer vacant. Housing is expensive. Child care is impossible to find." Even small towns are being affected. Especially on the Eastern Slope, small mountain towns and hamlets are becoming cities overnight. In Elizabeth, a town of about 1,400 people, new construction is raising concerns; one proposed development would build about 750 new homes, bringing an increase of about 1,900 people. If the political mood remains as it is today, Colorado's growth can be expected to continue and the state's population could easily reach and probably surpass the 6.4 million projected for 2025. The seven million mark, or even higher, could be reached by 2050. These numbers will impact nearly every aspect of life in Colorado.
 
Colorado school enrollment (K-12), which grew by 29 percent in the last decade, will continue to grow rapidly. In just ten years, the number of students could increase by over 100,000 - from 790,000 in 2000 to 900,000 in 2010. It could easily surpass one million by 2025. To maintain its 1999 student-teacher ratio, approximately 5,000 new teachers will have to be hired annually. Another 10,000 public school students per year means building at least 20 new schools every year. In Douglas County alone, a planning committee has estimated the county will need ten new schools in the next five years to keep up with its ballooning population. The Denver Rocky Mountain News reported that construction and renovation to ease overcrowding would cost 165 million to 175 million dollars.
 
Eleven percent of Colorado workers travel more than 40 minutes to work. If trends continue, the average metro area motorist will spend twice as much time in traffic by 2020.
 
During the 1990s, the population of metropolitan Denver grew from under 2 million to over 2.4 million. The Denver Regional Council of Government's (DRCOG's) growth forecast for 2020 predicts that more than one million more people will come to the metro area within the next 20 years. More than one in five of the new residents will live in Adams County, meaning Adams County will gain an average of 11,400 new residents a year. The Colorado Public Interest Research Group report on sprawl writes, "If we don't take action now, the metro Denver area is well on its way to becoming another L.A."
 
The Denver Post reports of pollution levels in Denver, which regularly violates the federal standards for ground-level ozone: "The brown cloud no longer is a winter phenomenon limited to Downtown, but a year-round problem blanketing the entire area." These problems extend beyond the metropolitan areas, as suburban sprawl contributes to increased air pollution throughout most of the state. Population drives water consumption as well. Colorado's fast-growing cities may eventually face water shortages unless local utilities find new supplies. The Governor's Commission on Saving Open Spaces, Farms, and Ranches found, "Rapid growth, inadequate water supply and extremely dry conditions have left cities thirsty for more water."
 
The Census Bureau's new projections indicate that immigration will account for two-thirds of all growth nationwide over the next century. In Colorado, most population growth comes from domestic interstate migration (people moving in from other states). Yet this is often caused by immigration (people moving in from other countries), through what is known as secondary migration. Secondary migration occurs when people leave crowded areas in search of more space. This is happening around the U.S., as massive immigration drives the native population to move to less crowded areas. Colorado has been a magnet for such migrants - notably, Californians trying to escape the effects of the states record population growth - growth that has been driven by high immigration levels. A full quarter of migration into Colorado in the past decade has come from California.
 
As long as federal immigration levels remain at their present non-traditional highs of nearly one million each year, the pressures that immigration puts on border states will continue to affect every state. On top of legal immigration is the pressure from illegal immigration; it is estimated that over five million illegal aliens reside in the U.S., and 300,000 new illegal aliens settle in the country each year. Colorado ranks eleventh in illegal immigration, with over 45,000 illegal aliens residing in the state as of 1996, the latest year for which numbers are available. If federal legislation limiting immigration to more traditional levels of 200,000 to 300,000 annually were passed and if illegal immigration were drastically reduced, migration levels into Colorado could be drastically reduced.

"If the political mood remains as it is today, Colorado's growth can be expected to continue and the state's population could easily reach and probably surpass the 6.4 million projected for 2025. The seven million mark, or even higher, could be reached by 2050. These numbers will impact nearly every aspect of life in Colorado."