I am new to crypotocurrency mining and I recently had an experience that I would like to ask about.

I short-term leased 100MH/s Scrypt hashing capacity and pointed it at a certain pool. I noticed the pool total was about 1.5GH/s at that time.

I watched it for 6-8 hours and I was making about a 30% profit over my costs. In that time I spent about 0.002BTC and had a balance on the pool of about 0.0025. So, convinced, I increased my hashrate to about 1GH/s and left it alone for several hours. After the increase I spent another 0.008BTC but my total earnings (for both timeframes) was only abut 0.0055BTC.

So after my increase I was a large portion of the pool's hashpower (about 40%). Does a pool reach a point of saturation where additional hashpower has no benefit?

I know that there can be diminishing returns on coin networks, but it would seem to me that I can't possibly have been a large portion of the worldwide Scrypt capacity, even though I was a large portion of the pool

Thanks,
Jacob