I'd rather look at it on the face of it rather than compartmentalise this based on months .... aside from the difficulty mined in certain periods, there is nothing to make a month's period any special to the bitcoin network. So here goes ...
I was only able to get data for the period 2015-01-08 18:50:01 to 2015-02-18 13:15:21 (i.e the last block) and we have:
53 Blocks where the Pool Scoring Hash Rate was below 9 Ph/s
66 Blocks where the Pool Scoring Hash Rate was above 9 Ph/s BUT below 9.5 Ph/s
23 Blocks where the Pool Scoring Hash Rate was above 9.5 BUT less than 10 Ph/sPh/s
23 Blocks where the Pool Scoring Hash Rate was above 10 Ph/s
True, When it hits the 10PH mark the blocks stop for regular users and the clock keeps running. However, behind the scenes a select VIP elite group are actually getting the same regular block times the rest of us were enjoying and splitting the rewards between them. Once they've creamed enough they then drop the hash rate below 10PH which synchronizes the system and the extra long block ends and normal service resumes.
Yes, I am crazy and I am aware I have opened the floodgates.
If you actually believe that drivel and think the pool op is actively screwing you, why don't you move elsewhere?