After I wrote about how well-off millennial renters are the biggest demographic in the Cook County housing market, someone asked me: What do all these people do, anyway, to afford such nice apartments?

I started with the American Community Survey. Six industries had median incomes above $70k in 2014. Overall, employment change in those industries has been positive, and the industries with positive growth shouldn't be terribly surprising—health care, computer and mathematical occupations, and management.

Jobs Paying More than $70,000

I also looked at employment change in industries where the median income is less than $50k in 2014. (A side note, but a telling one: they weren't the same industries in 2009. In 2009, Construction and sales had median incomes over $50k in 2014 dollars; in 2014, they had median incomes below $50k.) Employment fell precipitously in construction, office and administrative support, and production. It wasn't all bad news—employment in transportation grew substantially—but the ACS data suggests a decline in lower-middle income workers.

Jobs Paying Less than $50,000

But that doesn't account for age, obviously. For that, I used the powerful IPUMS (Integrated Public Use Microdata Series) database at the University of Minnesota's Population Center to slice up the numbers for millennial renters in the city of Chicago.

First, how many people in this age group are choosing to rent versus buying? I looked at people ages 25-34 with 2014 incomes of more than $75k, $100k, and $200k, via the 2014 American Community Survey, as compared with similar groups from 2009 (adjusting income for inflation).

2009, $68k+	2014, $75k+	2009, $91k+	2014, $100k+	2009, $181k+	2014, $200k+
63%	47%	68%	55%	66%	76%

The number of these high-income 25- to 34-year-olds is down overall (though it's more of a wash if you don't adjust the incomes for inflation). But dwelling habits have changed; a majority go from buying to renting, except at the top of the income bracket, where the most well-off millennials are more likely to buy than rent.

This seems to line up with what Chris Hagan and Daniel Kay Hertz have observed: In some of Chicago's wealthiest neighborhoods, lower-density apartment buildings are being torn down for single-family homes or luxury condos. Meanwhile, reasonably well-off but not wealthy younger adults are opting to rent, creating a market for the kind of high-end transit-oriented development John Greenfield writes about in Streetsblog today.

So what do these millennials do to make so much money? Again, I queried the IPUMS database, using the 2014 and 2009 ACS data. Here's what 25- to 34-year-old renters with individual (not household) incomes of $68k or more, again adjusting for inflation, were doing in 2009. I limited it to occupations with about 1,000 people.

Now, from the 2014 ACS:

First, there are now more occupations representing 1,000 or more renters, because there are more renters. And the changes seem to reflect broader economic trends. There are way fewer lawyers—in 2010, Crain's reported that "a parade of notable law firms in Chicago has laid off attorneys in the midst of the recession." There are more management analysts—in 2013, Crain's reported that "it's a good time to be in the consulting business." Marketing and sales managers held strong—last year, Forbes reported that "Chicago is still known as the place for finding the geniuses of the consumer packaged goods marketing sphere."

Based on the ACS data at least, Chicago's spate of high-end apartment development doesn't seem to be coming so much from more well-off younger adults, but from changing preferences in the housing market. If the Emanuel administration's planned downtown zoning changes go through, they'll have even more options closer to the city center, where 90 percent of its job growth came from 2002-2014. What remains to be seen is if the city can lock them in as residents, whether or not they're renters.