It's not 'short term', but a long term trend. Right now Antpool reports 57.77 PH/s. Your chart at
https://bitcointalk.org/index.php?topic=104664.0 shows that DiscusFish and Antpool found about 27% of blocks between Feb 8 and Feb 14. Isn't this simply a case of smaller pools like Slush having a smaller fraction of the overall hash rate?
Cheers
Oh, I see. No, the amount of blocks a block maker solves is related to the block maker's hashrate and the network difficulty, nothing else. In the long term of course difficulty will rise, and what you expect will happen. But in the short term it just means a larger number of blocks solved per day overall. Does that make sense? I know it's a bit anti-intuitive.