It's because the time-out ratio is based on the last 90 days. If you were very active from the start of that period, relative to your current activity, it might go up for a while, but then it will eventually go down as the period when you timed out will get out of that last 90 days.
Timeout rating
As I am completing matches, my timeout raing is going UP, even though I have not timed out in over a week... That's not cool...
It has to go up at first, as the non-timeout games you completed 90 days ago fall out of the calculation. You have to double or triple your efforts to complete games or simply wait 90 days for the timeout games games to fall out of the calculation.
http://www.chess.com/forum/view/help-support/time-out-percentage-101
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As I am completing matches, my timeout raing is going UP, even though I have not timed out in over a week... That's not cool...