To determine the top special interests lobbying in statehouses around the country, the Center for Public Integrity analyzed lobbying registration data from 2010 through 2014 collected by the National Institute on Money in State Politics.

The data include registrations for both in-house lobbyists and part-time hired guns. The Center consolidated subsidiary corporations under their parent corporations.

The Center’s top 101 national list is based on the geographic reach of the companies, trade associations and other special interests that employed the registered lobbyists. It includes entities that had lobbyists registered in at least two-thirds of the states at some point from 2010 through 2014. A lobbyist entity (sometimes called a lobbying principal or client) had to be active in a state in at least one of those years for that state to be included in the entity's total. In other words, the numbers on the list represent the approximate number of states the entity touched with its lobbying in a five-year period.

The Center determined the most active special interests in each state by analyzing which entities had the most lobbyist registrations from 2010 through 2014. The Center computed the ratio of lobbying interests to legislators in each state by using data collected by the National Conference of State Legislatures on the number of legislators in each state. The ratios are rounded to the nearest whole number.

The Center used historical data from its 2006 Capitol Offenders project for historical comparisons to 2000.