Among the nation's 25 largest markets, metro Atlanta rents rank 16th for affordability, according to a report out today.

The question of rental affordability is a key concern for millennials, as well as others.

Of Atlanta's rental listings in April, 55.9 percent were affordable, based on the area's median household income, according to Trulia, a San Francisco-based company that offers online housing information aimed at homebuyers, sellers, renters and professionals in real estate.

Rents matter to households, of course, but also to the region’s economic trajectory. Growth depends partly on attracting people, especially ambitious and skilled professionals. And many people who are new to a region rent.

Since the housing bubble burst in 2007, proportionally more households are renters, Along with that is the rising popularity of urban living.

The result of these and other economic factors has been a cultural shift: The millennials – who are often viewed as a crucial demographic for building future growth and prosperity – are more statistically likely to rent than previous cohorts of people were at a similar age.

For what it's worth, metro Dallas, often seen as Atlanta's chief economic competitor in the south, has a higher ranking: 71.4 percent of that region's listings are affordable, Trulia said.

But then, the measure of affordability is actually a comparison of two economic indicators: the rent and the area’s median income. More expensive rents are more affordable if more people are making more money.

It goes the other way, too. Some poor areas are affordable.

So a higher ranking doesn’t necessarily mean an area is more attractive and a better place to live. It just means the rents are low relative to incomes.

With that in mind, the top two metros for affordability were metro Newark, N.J., which includes portions of Pennsylvania, and St. Louis.

About 98 percent of apartments in metro Newark were affordable, as were 95 percent of those in St. Louis, Trulia said.

In contrast, only 7 percent of the apartments in the Miami region are affordable. Next lowest ranking is New York’s metro area, where 20 percent of rentals are affordable, Trulia said.

In Atlanta, the median rental price is about $1,350, an increase of 13 percent from last year, Trulia said. However, most of those listings were either in the city itself or in the near suburbs.