Sample Design

The NDTS sample was drawn in 2003 from the 2000 Census of State and Local Law Enforcement Agencies conducted by the U.S. Bureau of Justice Statistics.  After careful review of the more than 17,000 law enforcement agencies in the 2000 Census of State and Local Law Enforcement Agencies, a final sample frame of 7,930 state and local law enforcement agencies with drug law enforcement responsibilities was created.


Municipal police departments from every state, including regional and county police departments with 10 or more sworn full time equivalent (FTE) officers, were retained for the sampling frame.  County sheriff’s offices with 10 or more sworn FTE officers were also retained for the sampling frame except those in six states where county sheriff’s offices do not have drug law enforcement responsibilities.  In the rest of the country, sheriff’s offices were excluded if they did not indicate on the 2000 Census of State and Local Law Enforcement Agencies that they enforce drug laws.  Campus police departments, constables, and special police agencies were excluded since most of these agencies, too, have limited or no drug investigation responsibilities.  Tribal police departments, whose jurisdictions fall under federal authority, also were eliminated. State drug investigative agencies not in the 2000 Census of State and Local Law Enforcement Agencies were added to the sampling universe.


The sample frame of 7,930 state and local law enforcement agencies was stratified to include the following specific groups of state and local law enforcement agencies to ensure a thorough analysis of the domestic drug situation:

  • All municipal police departments and county sheriff’s offices with 75 or more sworn FTE officers as reported in the 2000 Census of State and Local Law Enforcement Agencies were selected with certainty for the sample.  This criterion ensures that all major cities and metropolitan counties are included in the sample.
  • State police and state-level investigative agencies were selected with certainty to provide information on the drug threat situation from a state perspective.  State police agencies were obtained from the 2000 Census of State and Local Law Enforcement Agencies.
  • Additional state-level investigative agencies were determined as a result of NDTS research.  Typically included for each state were the state police and lead drug enforcement agency, although this pattern varied in some states.
  • Investigative agencies in three U.S. territories—Guam, the Northern Mariana Islands, and Puerto Rico—were also included in the sample.
  • Municipal police departments and county sheriff’s offices with 10 or more but fewer than 75 sworn FTE officers, and meeting all the criteria discussed above, were selected randomly to ensure that state-level representative statements could be made about NDTS data obtained through the survey.

Each year, the sample is adjusted to account for agencies that cease operations or merge with other law enforcement agencies.  Several state agencies have been added to the sample since 2003.