Local Population Projections and Growth Expectations

November 2, 2018 | More News

Knoxville is growing and will continue to do so.

In the next few decades, we expect thousands of new residents to call our city home. The update of the city’s zoning ordinance will help prepare the community for that growth, striking a balance between protecting valued traits of existing neighborhoods and creating vibrant new communities to accommodate all residents.

With population growth comes demand for new community services, like transit and senior support programs, and infrastructure, such as schools and roads. Public investment should stay ahead of demand, a constant challenge in fast-growth communities. Population decline offers its own set of challenges, sometimes necessitating reductions in community services and infrastructure to ensure efficient stewardship of public resources. To predict growth or decline in the number of people living in a geographic area, planners turn to population projections.

Knoxville-Knox County Metropolitan Planning Commission has relied on three different sources of population projections for Knox County in recent years: University of Tennessee Boyd Center for Business and Economic Research (CBER), Woods and Poole Economics (WP), and Bernardin Lochmueller and Associates (BLA) (Figure 1). Each is different in underlying methodology, and predicted outcomes vary in some measure. Use of multiple approaches allows planners to consider a range of outcomes, often in scenarios of low, moderate, and high degrees of population change.

Figure 1. Three Population Projection Models for Knox County

Model

Knox County 2040 Population

Boyd Center of Business and Economic Research, 2017 (CBER)

543,334

Woods and Poole Economics, 2017 (WP)

579,272

Bernardin Lochmueller and Associates, 2012 (BLA)

621,702

MPC has consulted several releases of the CBER and WP models since 2012. (The BLA model was prepared only one time for the agency as part of its modelling work in transportation planning and for the Plan East Tennessee regional plan in 2013.) CBER and WP model inputs and methods change over time, relying on observed data and trends from the past to inform predicted trends of the future.

Lowered Expectations for County Growth

Since 2012, CBER and WP have decreased their rates of modelled growth for Knox County. The 2012 release from CBER projected total population at 566,175 by 2040, a 31.0 percent gain. Their 2017 edition lowered that prediction to 543,334, a downward adjustment to 25.7 percent growth (Figure 2). In similar fashion, WP’s 2012 model projected countywide population at 662,902 by 2040, a sizable increase of 53.1 percent. WP’s 2017 version downgraded that figure to 579,272, or 33.8 percent growth (Figure 3).

Figure 2. Center for Business and Economic Research Projections

Release

2010 Population

2040 Population Projection

Population Change

Rate of Change (%)

2012

432,226

566,175

133,949

31.0

2013

432,226

595,787

163,561

37.8

2015

432,226

584,406

152,180

35.2

2017

432,226

543,334

111,108

25.7

Figure 3. Woods and Poole Projections

Release

2010 Population

2040 Population Projection

Population Change

Rate of Change (%)

2012

433,108

662,902

229,794

53.1

2013

433,110

602,218

169,108

39.0

2015

433,041

602,851

169,810

39.2

2017

433,035

579,272

146,237

33.8

The underlying drivers of CBER’s projection model are births, deaths, and migration of residents, which are the only reasons a population can change. According to CBER, the decrease in projected growth is a result of the following structural changes:

(For more information on the Boyd Center’s projection model and its underlying components, see “Population Projections 2017: Methodology, Executive Summary, and Notes”)

While the rate of predicted growth has slowed, it is not to an extent that drastic, adverse impacts on population growth will be felt. Projection models are built on foundations of known information – trends in data from the recent past – but they also include an element of uncertainty, as does any endeavor to predict an unknown future. That said, we are confident that Knoxville and Knox County will continue to grow. The agents of change are still at work locally, expanding our city and county populations.

City Growth Expected to Accelerate

Over the next 20 years, Knox County’s population will reach a total somewhere between 543,000 and 579,000. The headline here, though, is that we will see gains in population in the City of Knoxville too. That is particularly noteworthy because that will buck a decades-long trend. Between 1970 and 2010, the city saw very little change, the bulk of local growth occurring in unincorporated portions of Knox County. In that time, city population fluctuated modestly from a low of about 170,000 in 1990 to a high of 179,000 in 2010 (Figure 4).

Sources: U.S. Census Bureau, Population of Counties by Decennial Census: 1900-1990, March 27, 1995;
U.S. Census Bureau, Census of Population and Housing, 2000 and 2010; and, U.S. Census Bureau, Population Estimates Program, 2018.

Since then, city population has seen rapid growth, adding nearly 8,500 new residents in the past seven years. The trend line in Figure 4 shows flat population change since 1970, but it masks the burst seen since 2010. The closer look depicted in Figure 5 reveals the growth. And that growth is claiming larger shares of countywide total population gains. Between 2000 and 2010, city increases contributed only a 9.9 percent share to total county growth. Over the past seven years, though, that impact has tripled to a 28.6 percent share (Figure 6).

Sources: U.S. Census Bureau, Population of Counties by Decennial Census: 1900-1990, March 27, 1995;
U.S. Census Bureau, Census of Population and Housing, 2000 and 2010; and, U.S. Census Bureau, Population Estimates Program, 2018.

Figure 6. Knoxville and Knox County Population Growth, 2000-2017

Period

Knox County Growth

Knoxville Growth

City Share of County
Growth (%)

2000-2010

50,194

4,984

9.9

2010-2017

29,634

8,473

28.6

Sources: U.S. Census Bureau, Census of Population and Housing, 2000 and 2010 and U.S. Census Bureau, Population Estimates Program, 2018.

Rise of the Millennials

What’s behind the resurgence in city population growth? Most notably, it’s Millennials. According to a recent report from the Executive Office of the President of the United States, Council of Economic Advisors, Millennials are moving into urban areas much faster than their predecessors, and they are less likely to be homeowners than young adults of previous generations. The recent boom in apartment unit construction in the City of Knoxville confirms this trend: in just the past five years, 2,908 apartment units were added to city housing inventory, compared to 920 single-family homes, apartments capturing a 76 percent share of new supply.

In addition to housing options in the city, Millennials are drawn to the varied transportation options (transit, ridesharing, bicycling), walkability, downtown energy, cultural diversity, and social amenities of urban living. We expect urban gains to continue over the next several years as the youngest Millennials move out of their parents’ homes into their own spaces.

We know city growth is underway, and more is expected over the next several years. We must plan for accommodation of that growth, and the overhaul of our outdated city zoning ordinance is an important step in that process.