Researchers have presented the first-ever comprehensive analysis of third-party web tracking across three decades and a new tool, TrackingExcavator, which they developed to extract and analyze tracking behaviors on a given web page. They saw a four-fold increase in third-party tracking on top sites from 1996 to 2016, and mapped the growing complexity of trackers stretching back decades.
Read more about the research out of U. of Washington on ScienceDaily.