Surely, something does not seem quite right about your numbers phillip, and surely we are seeing something like a 2x in that performance.

Of course, if you had lump summed into your paypal purchases of bitcoin coupons, your value would have gone up 4x to 5x from a kind of $12k-ish to something approaching $60k.. so the fact that you have something that is much closer to 2x seems to support that your purchases are a bit skewed in very recent times rather than earlier times of your getting involved with reporting your paypal purchases..

My suspicion is that your profits from mining, as measured in dollars, had gone up more in the second half of the measuring period rather than in the first half and so therefore, your injection of value into your paypal account to buy bitcoin coupons actually was skewed towards the later half rather than the first half of the measuring period.