I think you should rather compare the ratio investor's coins/total coins.
For example lets say you bought 1 zch and 1 piv and there were total 100 coins of both of them (You have 1% in them) 2 months ago.
Today you will still have 1 zch but the total zch will be 127 which means you will have less than 1%.
The total pivs will be 101 and if you are staking you would have 1.01 piv which is still 1%. (You would have even more because not everyone is staking).
I think you should not compare the price to usd because tomorrow zcash can be 300% up.