As a demographic, millennials have a lot going for them. They're young, connected, multicultural and there are an awful lot of them. Any number of brands count them among the most coveted segments to market to. But where are they?

Using Ad Age's new tool, Market Finder, we thought we'd find out. First off, let's define our terms. For the purpose of this piece we'll be looking at millenials as aged 18-34, and specifically at the older end of the spectrum, the 25- to 34-year-olds. For our geography we'll look at cities and their suburbs, or Metropolitan Statistical Areas in Census speak. Looking at sheer population, you rarely find anything unusual at the top end of a ranking. New York, Los Angeles, Chicago, Dallas and Houston have the most millennials, which makes sense as they are the five of the six largest metro areas in the U.S.

These are also the top five markets for late millennials -- and just about any other age group.

So let's look instead at concentrations. In the U.S. millennials make up about 23% of the population, with just more than 14% of that the older Gen Y folks who are out of college and starting to spend their own money -- assuming they have moved out of their parents' house, which a recent National Association of Realtors study found 13.4% of them have not. That's a 30-year high, by the way.

So again using Market Finder, it's easy to look at index values of the population, where is the population disproportionate to the U.S. figures. The highest index metros for millennials are all college towns or near military bases that don't have otherwise large, diverse population centers like "college towns" such as Boston. Jacksonville, N.C., has an index of 192, meaning its millennial population is almost twice as large as a typical city. It's home to the Marine Corps. base, Camp Lejeune.

The big cites, conversely, all hover right around the U.S. average in their indices.

The older millennials are even more interesting because those clusters do happen in cities with more balanced populations such as Austin, Salt Lake City, and Jonesboro, Ark. -- just over the state line from Memphis. The college towns listed above that index high for all millennials also index low for the late millennials, showing that once they graduate, they're not sticking around.

So if Austin were a typical metro area it would have 230,000 late millennials. Instead it has 322,300. A typical late millennial spends about 5% fewer dollars than a typical American, according to Bureau of Labor Statistics. But certain product categories they spend more, in some cases much more. They spend about $50 per capita more on alcoholic beverages, $400 more on personal services and nearly $100 more on furniture. They are more likely to have young kids, especially in Salt Lake City so they spend twice the national average on clothing for children under the age of 2.

All of this adds up to a lot of skewed market potential for certain brands.

We'll be pulling together posts like this for other consumer markets in the next few weeks. Next up, your big-spending married couples with children. What other markets would you like us to delve into?