Findings

Measuring Overall Sprawl (Loss of Habitat and Farmland)

This study focuses on the loss of previously undeveloped, or rural, land that includes cropland, pastureland, rangeland, forest, and other natural habitat and open space in the state of Colorado.
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Colorado Urbanized Areas and Developed Areas

Per Capita Sprawl and Overall Sprawl

Many respected environmental organizations and urban planners contend that implementing Smart Growth, New Urbanism, and LEED (Leadership in Energy & Environmental Design) building strategies into our new and existing cities is the best way to rein in sprawl in our cities. However, this is based on the premise that it is only or primarily our land-use choices that cause sprawl in Colorado.  As our multiple studies over the past two decades demonstrate conclusively, Per Capita Sprawl by itself could not explain Overall Sprawl in the great majority of America’s urbanized or developed areas.  

Colorado is no exception. 

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By comparing the percentage growth of per capita land consumption (Per Capita Sprawl) with the percentage growth of Overall Sprawl in the nine Urbanized Areas in Colorado from 2000 to 2010 (2020 data is not yet available), we find that the Per Capita Sprawl percentage is much smaller than the Overall Sprawl percentage: 4 percent versus 25 percent. This is not to denigrate Smart Growth, New Urbanism, and the LEED program, but to recognize their limitations when they don’t also focus on the role of population growth. These multi-faceted, multi-jurisdictional approaches have indeed slowed the pace at which sprawl is converting the countryside into pavement and buildings over the last decade. Given incessant population growth, however, they are capable only of slowing sprawl, not stopping it.
Recent Per Capita Sprawl vs. Overall Sprawl in Colorado UAs, 2000-2010
Note: Per Capita Sprawl is % growth in per capita urbanized land consumption and Overall Sprawl is % growth in urbanized land area.

Recent Per Capita Sprawl vs. Overall Sprawl

Colorado Urbanized Areas – 2000-2010

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This table compares the percentages of Per Capita Sprawl and Overall Sprawl from 2000 to 2010 in all nine UAs in the state of Colorado. In all cases but two (anomalies), Per Capita Sprawl is only a small fraction of Overall Sprawl. Per Capita Sprawl was non-existent (negative) in the smaller four of the nine UAs, but positive in the two largest UAs – Phoenix-Mesa and Tucson, though still much smaller than Overall Sprawl.
Urbanized Area% Change in Per Capita Land Consumption, 2000-2010 (PER CAPITA SPRAWL)% Change in Overall Land Consumption, 2000-2010 (OVERALL SPRAWL)
Denver--Aurora, CO 12%34%
Colorado Springs, CO -21%-5%*
Fort Collins, CO 2%31%
Pueblo, CO25%31%
Grand Junction, CO1%41%
Greeley, CO-3%22%
Boulder, CO-3%-1%*
Longmont, CO-7%-16%
Lafayette--Louisville--Erie, CO-4%26%
All Colorado UAs4%25%

Recent Per Capita Sprawl vs. Overall Sprawl in Colorado UAs, 2000-2010

See Appendix D (“Anomalies – Urbanized Areas with Populations that Grew But Areas that Supposedly Shrank”)

Even the best Smart Growth, New Urbanism, and LEED strategies are able to engineer only so much population density. As long as the population is still growing, the land area taken up by Colorado cities will almost certainly continue to grow.

Population Growth

Colorado is a prime example of what a seemingly modest annual growth rate can lead to if just given enough time.

State Sprawl

Colorado Population Growth from 1900 to 2020 and Projected to 2050

Source: U.S. Census Bureau (Census counts) and Colorado State Demography Office.

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A city or state’s population increases or decreases based on the net sum of the collective actions of millions of individuals and their personal choices and behaviors – births, deaths, and in- or out-migration (emigration) – as well as on local, state, and national governmental actions and policies.  Looking more closely, the net increase (or decrease) in population in any given time period (e.g., one year, one decade) is due to the number of births minus the number of deaths plus the number of in-migrants (immigrants) minus the number of out-migrants (emigrants).

In 1910, there were just over one-half million (543,000) residents in Colorado; after 120 years of nearly continuous growth, this number had exploded by more than 10-fold (i.e., more than an “order of magnitude” increase) to approximately 5.8 million. The fact that this function is generally curving upward suggests exponential growth for much of the period of record.  Overall, the average annual compound or exponential rate of increase over this 120-year period (1900-2020) was about two percent (1.98954% to be precise).

University of Colorado-Boulder, Professor Albert Bartlett (1923-2013)

Colorado is a prime example of what a seemingly modest annual growth rate can lead to if just given enough time. A mere two percent per annum growth rate steadily maintained for 35 years leads inexorably to an approximate doubling in the population size or number of any entity – whether dollars, wombats, widgets, or human beings.  These remarkable facts and many others related to the exponential function were the subject of more than 1,600 presentations on “Arithmetic, Population, and Energy:  Sustainability 101 given to audiences numbering collectively in the hundreds of thousands over nearly 50 years by the late University of Colorado-Boulder physics professor Albert Bartlett.

Population Growth in Colorado Counties 1982 - 2017

* Broomfield County, the newest and smallest county by area in Colorado, was carved out of Boulder County in 2001; for the purposes of this study its population and small area are included with Boulder County

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This map shows the population change in all Colorado counties from 1982 to 2017. On average during those 35 years, these 64 counties (including Broomfield, lumped in with Boulder) grew by 83 percent; that was an annual compound (exponential) rate of 1.75 percent.  The populations of 46 of Colorado’s 64 counties increased, while 17 decreased, and one (Bent County) underwent essentially no change (just 12 fewer residents in 2017 than in 1982).The map covers a period that starts in 1982 when the first federal NRI results were published, and ends in 2017, the year of the last available data at the time of this report.

Unsurprisingly, the greatest population growth occurred in counties along the Front Range of the Rockies:  El Paso, Arapahoe, Douglas, Adams, Denver, Boulder, Larimer, and Weld.

This map shows the population change in all Colorado counties from 1982 to 2017. On average during those 35 years, these 64 counties (including Broomfield, lumped in with Boulder) grew by 83 percent; that was an annual compound (exponential) rate of 1.75 percent. The populations of 46 of Colorado’s 64 counties increased, while 17 decreased, and one (Bent County) underwent essentially no change (just 12 fewer residents in 2017 than in 1982).

The map covers a period that starts in 1982 when the first federal NRI results were published, and ends in 2017, the year of the last available data at the time of this report.

Unsurprisingly, the greatest population growth occurred in counties along the Front Range of the Rockies: El Paso, Arapahoe, Douglas, Adams, Denver, Boulder, Larimer, and Weld.

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Population Growth in Colorado Counties 2002 - 2017

[INTERACTIVE COUNTY MAP #2]

This map shows the more recent sub-period from 2002 to 2017. The aggregate population of Colorado’s 64 counties increased by 25 percent during these 15 years, at an annual compound (exponential) rate of 1.5 percent, almost identical to (but slightly slower than) the percent (1.6) during the larger 35-year period from 1982 to 2017.

The populations of 45 counties increased while 19 decreased. While the rate of annual percentage increase (1.5%) in this most recent period was a bit lower than the average annual percentage increase over the entire 35-year period of record (1.6%) for NRI developed land in Colorado, the difference in the annual increment (average number of people added yearly to Colorado’s population) was the opposite. A few more residents were added annually between 2002 and 2017 (74,765) than were added annually per year between 1982 and 2017 (72,866).

Population Growth in Colorado Cities

In the 2000 and 2010 censuses, Colorado had nine delineated Urbanized Areas (the data for the 2020 census has not been released). These cities grew in aggregate by 20 percent in the single decade from 2000 to 2010.
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Population Growth in Colorado Counties, 1982-2017
County Total Sprawl 1982 to 2017 (square miles) % of Total Sprawl Related to POPULATION GROWTH % of Total Sprawl Related to GROWTH IN PER CAPITA LAND CONSUMPTION
TOTAL SPRAWL 1,206.4 100 0
WEIGHTED AVERAGE** 1206.4 86 14
 

***[Urbanized Areas – DATA TABLE for now]***

***NOTES from Jeremy

Keep this one as a table (for now — we’ll consider a map when the 2020 data is available).

Can we make it a 2-row table with just the header and the final row, but…

…make the first column a drop down where you can open up the middle nine rows?

[INTERACTIVE MAP #3,4??]

Nowadays, rapid growth in an urban area’s population is much more likely to be the result of enticing residents to relocate from elsewhere. Local and state governments can and do create many explicit incentives or subsidies that encourage people to move into a particular urban area. These include aggressive campaigns to persuade industries and corporations to move their factories, offices, headquarters, and jobs from another location, public subsidies for the infrastructure that supports businesses, tax breaks, expansion of water service and sewage lines into new areas, new housing developments and new residents, and general public relations that increase the attractiveness and “business friendliness” of a city to outsiders and the business community.

Even without trying, a city can attract new residents, especially if the nation’s population is growing significantly, as continues to be the case today. just by maintaining amenities, good schools, low crime rates, pleasant parks, and a high quality of life

Sources of Colorado's Population Growth

Colorado’s population has doubled between the 1980 and 2020 Censuses with growth being particularly rapid between 1990 and 2010. The State Demography Office projected in 2021 that Colorado’s population would reach 7.6 million in 2050.

Colorado Population by Decennial Census, 1980 to 2020

 

Year

Population

1980

2,889,964

1990

3,294,394

2000

4,301,261

2010

5,029,196

2020

5,773,714

2050 (projected)

7,564,742

In one form of analysis, all of Colorado’s population growth from 1982 to 2017 can be measured in two sources:
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1 %
from Natural Increase:
births in the state minus deaths in the state
47% Natural Increase
-
53% Net Migration
99 %
from Natural Migration
number of people who moved into the state minus those who moved out of the state
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“A little more than half (53%) of Colorado’s population expansion was due to people moving into the state while significantly fewer moved out during that period. The in-migration counts people who moved to Colorado directly from abroad and people (both U.S.-born and foreign-born) who moved into Colorado from other states.”

Percentage of Population Growth in Colorado Due to Natural Increase and Net Migration from 1982 to 2017

More recently, migration has become a much greater source of population growth in Colorado.

Percentage of Population Growth in Colorado Due to Natural Increase and Net Migration from 2000 to 2017

Like other western states who have seen rapid population growth, Colorado has taken in an influx of migrants from California, which has experienced many negative quality-of-life developments stemming from its own massive population growth in recent decades. However, Colorado has attracted residents from across the United States, many moving long distances to relocate in the Centennial State.

Top 10 Sending States to Colorado.

 

1.

California

2. 

Texas

3. 

Florida

4. 

Arizona

5. 

Illinois

6. 

New York

7.

Virginia

8. 

North Carolina

9. 

Georgia

10.

Missouri

Another way to measure a state’s population growth is to divide all growth between these two sources:

  • 26% related to international migration.
  • 74% all other sources.

Percentage of Colorado Population Growth Due Directly and Indirectly to Foreign Immigration, 1982 to 2017

PIE CHART

26% of Colorado’s population growth from 1982 to 2017 was due directly and indirectly to immigration from foreign countries. (read more…)

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This is based on the increase in the number of foreign-born residents and their U.S.-born children in Colorado, whether they came directly from another country or first settled in another state. Because births to foreign immigrants would not have happened in Colorado if not for the foreign migration, those births are counted in growth related to international migration.

 

The pie chart above is based on an analysis of the public use files of the 2017 American Community Survey (ACS) and the 1999 and 2017 Current Population Survey Annual Social and Economic Supplements (CPS ASEC).

 

Our estimate of immigration’s impact on Colorado population growth between 1982 and 2017 is based on an analysis of the public use files of the 2017 American Community Survey (ACS) and the 1999 and 2017 Current Population Survey Annual Social and Economic Supplements (CPS ASEC). It is well established that these Census Bureau surveys capture both legal and illegal immigrants.  The ACS and CPS identify immigrants (also called the foreign born) and ask what year they came to the United States. We use the ACS to measure the number of immigrants living in Colorado who entered in 1982 or later. In addition to identifying immigrants and their year of arrival, the CPS also asks each respondent the birthplace of their parents, allowing us to measure the progeny of post-1982 immigrants in the state. 

The 2017 ACS shows 466,000 immigrants living in Colorado who arrived in the country in 1982 or later. This number has been adjusted to exclude half of those who indicated in 2017 that they arrived in the year 1982.  This is necessary because the ACS and the population estimate on which overall state population growth is based reflect the population on July 1 of each year. However, the ACS measures immigrant arrivals by calendar year. In addition to immigrants who arrived in 1982 we also find based on 2017 CPS ASEC that there were 125,000 U.S.-born children (under age 18) of post-1982 immigrants in the state.  (We exclude those with only an immigrant father to avoid double counting.)  As these children still live with their parents, estimating their number is straightforward.

To estimate the number of U.S.-born adults in 2017 with post-1982 immigrant parents, we use the 1999 CPS ASEC.  In 1999 these individuals were still minors and lived with their immigrant parents.  In 1999, 51 percent of second-generation children born 1982 to 1999 with a foreign-born mother were the child of a parent who came in 1982 or later.  The remaining U.S.-born second-generation Americans in this age group were born to immigrant parents who arrived prior to 1982. Applying this percentage to the adult children of immigrants 18 to 35 in 2017 means there were 60,000 U.S.-born adult offspring of post-1982 immigrants in Colorado.  

Finally, we find that there were 22,000 minor children with second generation parents who are 15 to 35 in 2017.  These second-generation parents are old enough to have a child, but young enough to have been born to a post-1982 immigrant.  We again assume that 51 percent of these second-generation parents are the offspring of a post-1982 immigrant giving us an estimated 11,000 U.S.-born grandchildren of post-1982 immigrants in Colorado in 2017.  

In sum, we estimate there were 662,000 post-1982 immigrants, their children and grandchildren in Colorado in 2017.   The state’s total population was 3,045,000 in 1982 and 5,617,421 in 2017.  Immigration therefore accounted directly and indirectly for 26 percent of the 2,572,421 increase in Colorado’s population over this time period.  Thus, 74 percent or about three-quarter of the state’s population growth was due to domestic (non-foreign) sources, namely natural increase (births minus deaths of the native-born) and interstate migration (net migration to Colorado from other states).



Per Capita Land Consumption

Per capita land consumption statistics are a useful way to understand the combined power of numerous land use and consumption choices that can lead to urban sprawl.  

When Census Bureau data show that per capita land consumption was 0.18 acre in 2010 in the Denver-Aurora Urbanized Area, it means that it takes a bit less than one-fifth of an acre to provide the average Denver-Aurora resident with space for housing, work, retail, transportation, education, religious assembly, government, recreation, utilities, and all other urban needs.

Looked at another way, the per capita land consumption of a city or a county is determined by dividing all the developed acreage by the total number of residents. The lower the per capita consumption number, the more efficiently the population is using the land for urban purposes.

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Per Capita Developed Land Consumption

Per capita land consumption statistics are a useful way to understand the combined power of numerous land use and consumption choices that can lead to urban sprawl.  

When Census Bureau data show that per capita land consumption was 0.18 acre in 2010 in the Denver-Aurora Urbanized Area, it means that it takes a bit less than one-fifth of an acre to provide the average Denver-Aurora resident with space for housing, work, retail, transportation, education, religious assembly, government, recreation, utilities, and all other urban needs.

Looked at another way, the per capita land consumption of a city or a county is determined by dividing all the developed acreage by the total number of residents. The lower the per capita consumption number, the more efficiently the population is using the land for urban purposes.

Per Capita Land Consumption

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At a minimum, the per capita land consumption figure reflects the combined outcome of all the following individual and institutional choices and factors:
  • Development
  • Consumer preferences for size and type of housing and yards
  • Developer preferences for constructing housing, offices and retail facilities
  • Governmental subsidies that encourage land consumption, and fees and taxes that discourage consumption
  • Quality of urban planning and zoning
  • Level of affluence
  • Size of the entire built-up urbanized land area comprised of non- residential land uses, such as industrial, institutional, government, commercial, etc. 
  • Transportation
  • Governmental subsidies and programs for highways, streets and mass transit
  • Consumer preferences favoring the mobility and flexibility offered by using private vehicles rather than public transit
  • Price of gasoline (cheap gas encourages sprawl)
  • Quality of existing communities and ability to hold onto their residents
  • Quality of schools
  • Reality and perceptions concerning crime and personal safety
  • Ethnic and cultural tensions or harmony
  • Quality of government leadership
  • Job opportunities
  • Levels of pollution
  • Quality of parks, other public facilities and infrastructure
  • Number of people per household
  • Marriage rate and average age for marriage
  • Divorce rate
  • Recent fertility rate
  • Level of independence of young adults
  • Level of affluence enabling single people to live separately