This is going to be a quick analysis where I attempt to answer a question in what basically looks like the first pass I’d do for a larger research project. The goal is not to conclusively answer the question I pose, but rather to show how you could go start exploring a question like this and get at least some evidence and see if this is worth exploring further.
Research question
Hypothesis: Higher housing costs are associated with longer commute times. I came across this idea in a newsletter I got this week that was looking at commute times in cities around the world. The author included the following sentence which got me thinking: “Transportation researchers often say a city's average commute tells you almost as much about its housing market as its roads.”
The logic behind this hypothesis is that when housing costs are high, people have fewer options for housing in their price range. Less housing choices may lead to more people living farther away from where they work, which leads to longer commute times.
Methods
I’m going to use American Community Survey data for every metropolitan and micropolitan statistical area in the United States. I’ll collect their average commute time and their average housing cost and I will check the scatter plots to see if there are any obvious trends. Then, we can do a simple linear regression to see if those trends are statistically significant.
Because of the COVID-19 pandemic, I’ll do the regression on two samples: the 5-year ACS estimates from 2024 and from 2019. I suspect that if there is a trend, it is likely to be much stronger before the pandemic made working remotely significantly more common.
Results
Both scatter plots appear to have a slight positive trend, though the effect size is likely quite small. Both linear regressions confirm this first glance and find that there is a statistically significant positive correlation between housing costs and commute times. The fact that both of these results are positive and statistically significant does provide some early evidence that our hypothesis is true. The regression using the most recent 2024 data suggests that commute times increase by an average of one minute for every $500 of increased monthly housing costs. Note that the median housing cost in the 2024 data was about $1,000 per month and the max was about $3,000, so there is not a ton of variation on average.
Figure 1: 2024 housing and commute times by metropolitan area
Looking at the 2019 data, we find that commute times increase by an average of one minute for every $250 of increased monthly housing costs. It is hard to tell because the two plots aren’t overlayed but the slope of that two lines is essentially twice as steep implies basically double the impact. This supports the prior hypothesis that the COVID-19 pandemic weakened the correlation between housing costs and commute times. An alternative hypothesis as to why the effect is weaker today than in 2019: rising housing prices nationwide has made the baseline cost for housing higher, so marginal increases in housing prices have less of an effect on commutes than they used to in a 2019 world of lower baseline housing costs.
Figure 2: 2019 housing and commute times by metropolitan area
Limitations
This is not a causal analysis. This is not enough evidence to claim that higher housing costs cause people to have fewer options when it comes to where they live and therefore live farther away from their work. Notably we aren’t controlling for any other factors that might influence how long commutes are or how high housing costs are.
Another limitation is that I’m just looking at average housing costs and commute times across metropolitan areas. I don’t believe this is necessarily the best way to capture the relationship that I’m interested in, and maybe it would be better to look at individual level data.
Preliminary conclusions and next steps
Based on these regressions, I would say there is definitely evidence to support this hypothesis and it would be worth exploring further in a more concrete way. A good next step would be to see if there are any historic examples of natural experiments that could be exploited to better identify a causal effect.
