How about a chart showing RAC as reported at the daily update each day for the past 60 days, in addition to the chart of just credit by day? Should be easier to see trendlines that way, as credit can fluctuate a great deal from one day to the next - especially if you're crunching for projects w/ multi-day WUs (or server problems such as SETI recently had). I think this would function (and be useful) in much the same way as a moving average line on a stock price chart.

Added this for users and teams. Countries (and maybe hosts) will follow.