Table 1. Years and states included in analysis.

States	Years included in analysis
AZ, AR, CA, CO, CT, FL, GA, HI, IL, IN, IA, KS, KY, ME, MD, MA, MI, MN, MO, NE, NV, NH, NJ, NY, NC, OH, OK, OR, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY	2007–2011
AK, MS	2010–2011
LA, PA	2008–2011
MT, NM	2009–2011
DE, ND, ID, AL, DC	Not included