increments by which

I had to think of this in order to be able to phrase it at all. Could you read it and tell me if you understand it, and if it needs to be fixed?

The more shots you miss the smaller the increments by which you percentage drops/the less your percentage drops. If you take 1 shot and you make it you are 100% if you miss the next one you are 50% the one after that 33%, after that 25%, 20%,