What I can see is that you have taken the combined charts with ASICS. Was there any mining happening using BOINC during this period of time (green line in chart below)? For example team Bitcoin Australia was active from August-14 till July-16 where their credit went up from 0 to 69B and they have since then stopped. Another team following a similar pattern is mining@EVGA.

Analysing the overal BOINC credit chart below, the steep increase is for a period of 3 years (green line). Before and after this period, the increase looks similar and more muted (2 red lines).