here are the hardball times articles that I mentioned.
First, explaining the methodology:
http://www.hardballtimes.com/examining-potential-mlb-expansion-cities-part-1/1) Cities with higher incomes and lower levels of poverty draw more fans
2) Cities with a higher percentage of black and/or Hispanics/Latinos draw fewer fans
3) After accounting for income, cities with more college-educated individuals draw fewer fans.
4) Cities with a higher percentage of males draw more fans
5) Warmer cities tend to draw more fans
6) Cities with an NFL team draw fewer fans, but the hit isn’t as big if the city also has an NBA team
7) Cities with older populations tend to draw more fans
There's explanations for each of these factors in the article. The caveat with older populations is that cities with more 65+ fans do well on TV but worse on live gate. Hello, Tampa Bay.
The second article focuses on US cities without teams currently first, then discusses NYC/LA/CHI, and also international cities.
http://www.hardballtimes.com/examining-potential-mlb-expansion-cities-part-2/Top 5 are San Jose, by a lot, then Vegas, Austin, Sacramento, and Providence. He throws in the reality check of how the minor league teams draw.
San Jose has it all. But for the Giants blocking the city, it is ideal in almost all respects. Overeducated is the main drawback.
Vegas is heavily male, warm, and populous, but reality is that there may be too many distractions. Austin does very well, and I think is the most interesting city that is not usually talked about. Round Rock draws very well, Austin is one of 3 cities > 50% male (the others are #1 and #2), lots of money floating around, climate, and older but < 65. Sac'to is something of a surprise because it is never mentioned as an alternative to San Jose. In addition to the demographics, the River Cats are a great draw. This could be an alternative landing spot for the As if San jose is not feasible. Providence is just a weird result, but it gets helped in part because median age is 39+ and it is, to say it directly, very white.
There are some nice critiques of the analysis in the comments. Many point to Charlotte as being close to a number of population centers outside the MSA. Providence might be a result that should lead to skepticism about the methodology. That said, the skepticism about some cities like Indy and Portland is interesting, and flagging Austin I think is a nice bit of sifting data to come up with an option that should get some attention.
Portland does have a few things going for it. Like Charlotte, its age demographic is ideal. It also has few black and Hispanic residents, which bodes well for the city’s attendance figures. However, the city rates no better than average in every other category, with its cold climate acting as its biggest detractor.