If I have a specific Federal Code and I want to find a rough estimate of (1) how many people were charged with breaking that specific law, and (2) how many people were convicted under that specific law, where can I go to find those figures? Any help is appreciated.
The administrative arm of the judicial branch of the federal government publishes regular reports on criminal case loads here. For example, the statistics on criminal cases filed by offenses through December 31, 2021 can be found here. And the statistics on criminal cases terminated by offense and type of disposition can be found here. These tables break the offenses handled in the federal court system down into about 100 categories and are available for geographic subregions of the U.S. (particular district courts and particular court of appeals circuits). This is reasonably specific in a system than handles about 57,000 criminal defendants in a typical year.
The federal bureau of prisons likewise published regular statistics on who is detained for which offenses.
The U.S. Sentencing Commission also issues some relevant and useful reports with information not available elsewhere. For example, there is a report summarizing sentencing data in the 10th Circuit of the U.S. Courts of Appeals for 2021 that breaks offenses down into 30 categories with data on the number of offenders charged, the number of plea or go to trial for each of these 30 categories, the type of sentence imposed (e.g. probation, fine, prison), mean and median sentence lengths, and other data.
Many state court systems likewise published annual reports regarding their case loads, and many state corrections departments likewise publish regular reports regarding inmates serving sentences for crimes.
The information that is available is not generally as granular as a specific criminal statute. At the federal court level, offenses charged and tried are broken down into about 100 categories, with selective more finely detailed break out detail in some reports, and the federal bureau of prisons data is less fine grained than that. Some U.S. Sentencing Commission data is more specific, some is less specific.
Every once and while, usually for purposes of estimating the budget impact of proposed legislation, researchers, especially in the Congressional Research Service, the House and Senate Judiciary Committees, the relevant appropriations committees of each house of Congress, the Congressional Budget Office, or the Office of Management and Budget in the White House office, will contact administrators in the relevant federal agencies and get more fine grained data which is necessary for more accurate estimates for legislative purposes and is released in reports that they issue related to that legislation. But that is piecemeal and is not available comprehensively.
Sometimes academics and journalists and political action oriented interest groups and think tanks also estimate these numbers in academic journal articles, either with this kind of insider data or with a representative sample of cases (sometimes obtained with a Freedom of Information Act request). Every once and a while, you will see some relevant statistics in a U.S. Supreme Court amicus brief.