The numbers are based on the most conservative numbers possible using thorough original research of tens of thousands of staff who have appeared in congressional salary data since Oct. 1, 2000, as well as tens of thousands of lobbyists who have registered with the government since 1999. Not included are others who work for companies in the influence business but where the person does not register as a lobbyist.
A relatively small number of people who have made the trip through the revolving door multiple times may be listed more than once. A comparison of absolute numbers are not strictly possible because the amount of prior-year data is greater in later years.
Our party classification is based on the person's prior work history, not party registration, political donations or other evidence.
Committee staff were assigned based on whether they worked for the majority or minority. If a person's job history involved working only for one party, that party was assigned - even if the person was an intern or junior staffer. However, if the person worked for both Democrats and Republicans, junior non-policy positions were ignored.
People who worked only for administrative offices in Congress were not assigned a party unless they worked in senior appointed positions where they worked only for one party. For staffers of members of Congress who switched parties, a party was assigned if they worked for the member only before or after the party switch, or if the their employment history was consistent otherwise.