Tiobe seem to alter their methodology fairly often which afaik also has the effect of altering historical rankings. In other words if you look at the TIOBE rank

Tiobe seem to alter their methodology fairly often which afaik also has the effect of altering historical rankings. In other words if you look at the TIOBE rankings on the wayback machine for a particular year in the past they can differ greatly from the rankings for that year given on the site today. For example, I think that VB was affected greatly by this