I just made an observation that may be significant. When I save my games I put the year and month into the save name (e.g., 2189 July). After saving the game (I usually do this at end of turn, and I have autoturn off) I went to check an old bug (crash when all minors gone and selecting minor races from the foreign policy screen) and it crashed. When I loaded the game this time I looked carefully at the date, and it was a month later. Not only that, but I had another completion. On reflection, I believe I have seen the extra completions on restarting a game before, and I rember being pussled about a restarted game being at one month later than what I thought I had saved. If the values for these charts are kept in tables and it looks like one month of data is missing, couldn't it cause the downward spikes we see after reloading a game?