Note: Club Log's DXCC analysis feature (under the Tools > DXCC Analysis) page uses raw data which is periodically prepared in a more condensed form for reporting. Please be aware this data is not real-time and will generally be rebuilt every few months. Non-whitelisted entities are also subject to bad logging etc. so some internal noise floors are applied before this data set is published.
To access the information on this page via the API, you can use:
/dxcc_activity_api.php?api=[API key]
Data returned is a JSON array of each DXCC entity, a year (since 1980) and count of QSOs in that year.