The College Scorecard first released institutional-level earnings data in 2007-8 and continued releasing the data until 2015-6. At that point, earnings data started being measured. The following year, the first of the 1-year degree-level earnings data was released. The 2-year degree level earnings were released the year after that.
The College Scorecard has stated that they intend to release longer time periods as the data becomes available.