Here are the MKE traffic stats for January 2012

Market share by carrier:

……. 2012 …….. 2011
....34.8% ….. 31.8% ……. AirTran
....19.1% ….. 30.1% ……. Frontier
....16.7% ….. 14.7% ……. Delta
....12.5% ……. 9.2% ……. Southwest
......7.6% ……. 6.1% ……. United + Continental
......5.4% ……. 4.0% ……. USAirways
......3.3% ……. 3.3% ……. American
......0.3% ……. 0.2% ……. Air Canada
......0.2% ……. 0.4% ……. Other

2012 and 2011 traffic numbers:

…….. 2012 …….. 2011
….. 209,991 ….. 225,016 ……. AirTran
….. 115,296 ….. 213,253 ……. Frontier
….. 100,614 ….. 104,315 ……. Delta
….... 75,251 ……. 65,016 ……. Southwest
…….. 45,651 ……. 43,321 ……. United + Continental
…….. 32,592 ……. 28,613 ……. USAirways
…….. 20,065 ……. 23,097 ……. American
………. 1,704 ………. 1,714 ……. Air Canada
………. 1,432 ………. 3,220 ……. Other

Year--over-year change in passengers ranked. Note that some of the carriers (like Delta) with a greater market share still carried fewer passengers in 2012 than 2011, but did not shrink as fast as the overall airport.

…. -97,957 ……. Frontier
…. -15,025 ……. AirTran
…… -3,701 ……. Delta
…… -3,032 ……. American
…… -1,788 ……. Other
………… -10 ……. Air Canada
…….. 2,330 ……. United + Continental
…….. 3,979 ……. USAirways
…… 10,235 ……. Southwest

Finally, here are the totals for MKE as a whole, plus the four previous years to see how they compare.

2012 ….. 602,596
2011 ….. 707,565 ….. 2012 is 14.8% lower than 2011
2010 ….. 681,565 ….. 2012 is 11.6% lower than 2010
2009 ….. 487,279 ….. 2012 is 23.7% higher than 2009**
2008 ….. 596,732 ….. 2012 is 1.0% higher than 2008

**(YX made big cuts Sept 08, and FL still suspended east-west operation for winter then)

When I did a quick run of capacity for summer (I used a weekday in July) it looks like Frontier will be at about 10.5% Milwaukee market share.