Introduction
In the past, urban growth projections in the U.S.
traditionally relied on the basis that people move to where jobs are available
(Graves et al 2020, 323). However, some
recent trends have indicated that this relationship is no longer causing urban
migration. The researchers in this
article attempted to determine whether it is still happening, and whether there
is a variation between metropolitan size and economic base (ibid. 324). They determined this by using statistical
methods to evaluate population and employment data for 50 large metropolitan
areas in the U.S. (ibid. 324).
Literature Review
According to several studies, the expectation that
population growth should be proportional to job growth has become outdated
(ibid. 324-325). Recent studies on the
topic indicate that a behavioral shift has occurred, showing how more people
are migrating to cities for a better quality of life and not necessarily better
jobs (ibid. 325). Most studies have
shown that jobs follow people rather than the other way around (ibid. 325),
however they did not involve spatial parameters that would explain regional
variation. A statistical analysis of the
deviation between a metropolitan city’s jobs-population relationship can help
identify spatial patterns in urban growth projections.
Background and
Geographical Context
Most
of the cities evaluated were in top 50 U.S. metropolitan areas by population,
including New York, Boston, and Houston.
Data for the cities was retrieved from the U.S. Bureau of Economic
Analysis (ibid. 326), a government organization that has only been keeping
track since 1970. The date range for
this study started from the same year it was organized: 1970-2017 (ibid. 326).
Methods Used
Standard deviation and regression analysis
were used in the study (ibid. 327). Standard
deviation is a measure of the distance that a variable value is from a
statistic- usually the mean, or average (Gomez & Jones 2010, 286-287). Values below the mean are negative, while
values above it are positive. Standard
deviation is the most common measure of interval/ratio data (ibid. 287), which
is the type used in the study.
Regression
analysis measures the strength of correlations between variables on a number
line. It is an equation of the line that
best fits a scatterplot of the data (ibid. 301). Measuring the predicted change in one
variable (i.e. Y) as the value of another (i.e. X) changes is called the slope
of the line (ibid. 302). The slope,
along with the Y-intercept, can then be used to predict values for which there
isn’t any data on a graph. Multiple
variables can be used to evaluate the strength of their relationship to a
common variable (ibid. 304-305), simply by adding their coefficients (slopes)
to the equations.
In
the study, secondary data from the U.S. Bureau of Economic Analysis was
filtered to exclude age groups that aren’t typically in the job force (i.e.
infants and elderly). Cities were
evaluated based on the frequency of standard deviations from the EMP/WAP ratio mean
(Graves et al, 327). The EMP/WAP is the
employment to working age population ratio, which has historically been a
useful predictor of population growth (ibid. 326). The regression analysis was a test of the
long-term EMP/WAP relationship between the 50 cities and the entire U.S. population
mean (ibid. 327).
Analysis and Discussion
Using regression analysis, the researchers found a
weakening in the linkage between job creation and population growth of U.S.
cities (ibid. 330). The last two decades
(2000s and 2010s) showed stronger deviations than the previous three (1970s through
1990s). The education level of citizens
showed a strong correlation in cities with higher deviations above the mean
(ibid. 329), indicating it was the best predictor of a city having more jobs
per working age person.
While support for the statement that people are no longer
moving to urban areas for jobs is shown in the study, it wasn’t as successful
at explaining the spatial patterns found.
It appeared from the map provided that northern cities were more likely to
have higher deviations above the mean, with southern cities having lower
ones. Yet it is stated in the article
that this diversity appears heterogenous (ibid. 330). Providing statistics on this information
would have helped explain it better, and supported the article’s title more
since it mentions spatial change.
Statistical
methods can provide powerful insights into the relationships between
variables. One drawback of using
standard deviation is that it can be sensitive to extreme outliers (Gomez &
Jones 2010, 287), particularly when the data set is small. A problem with regression analysis is that a
correlation isn’t the same as causation (Gomez & Jones 2010, 306). Though a strong relationship may have been
found, it’s possible that there was an even stronger variable(s) left out of
the study that would have supported causation more.
For
instance, a big factor ignored in this study could be the percentage of jobs
that are service-oriented as opposed to industry and manufacturing. One change in the U.S. economy last century
was the transition from a manufacturing economy to a service one (Harris, 2020). With steady jobs in plants and factories
being replaced by retail and hospitality positions, people were more likely to find
part-time work, which was also exacerbated by recessions. Service economy jobs also include professional
ones in business and education (ibid.), which may be why the education finding
was most significant. If the regression
analysis had included service jobs as a factor, it might have shown this as a
strong relationship in spatial change between cities.
Conclusion
Statistics is a
good research method to use if the researchers are examining the right
variables. A conclusion can be falsely
drawn if they are not. Finding the right
variable may even be the point, which is why multivariate regression is so
useful. On the chance a key variable is
missed, the research won’t have as strong a conclusion. In this study it wasn’t as important to find
the why as much as it was answering the question, Are jobs still
bringing people to cities? Standard
deviation and regression did answer this, but it leaves the reader wanting
more.