This is my first year having a pool, and TFP has been a great resource. I initially set my CYA around 50 (in May). Now it is about 30. I have not worried about it too much, but why am I losing that much? I don't think splash-out explains it, because (according to the calculator) I'd have to lose over 13,000 gallons. My estimate is that I could potentially lose that much due to evaporation, but splash-out seems unlikely.
A sort-of related question. What should I target for CYA? My pool gets sunlight about 90% of the day, so I went toward the high end of the scale.