Hey guys, mod of r/AskEngineers here with a question that will hopefully allow me to assist our users better with the tons of career & relocation questions we get.

One of the most common questions asked by job-seekers is what the median salaries are for a given job / location, which is answered by a combination of BLS data and Glassdoor. I think that's fairly straightforward.

Part of that question that I haven't been able to answer in the past is how to directly compare costs of living between two locations — that is, until I remembered BEA and read their news release on Real Personal Incomes, which includes a short discussion of regional price parities (RPPs):

For example, if the RPP for area A is 120 and for area B is 90, then on average, prices are 20 percent higher and 10 percent lower than the U.S. average for A and B, respectively. If the personal income for area A is $12,000 and for area B is $9,000, then RPP-adjusted incomes are $10,000 (or $12,000/1.20) and $10,000 (or $9,000/0.90), respectively. In other words, the purchasing power of the two incomes is equivalent when adjusted by their respective RPPs.

What's less clear to me about this is whether direct comparisons outside of income are valid using delta-RPP as a ratio.

Suppose I want to compare rent between two metropolitan areas. Can I take one the delta-RPP divided by 100, and multiply it by the average cost of rent in area A to predict the average cost of rent in area B? (Example here)