Anyone else notice that over the past 2 weeks your share has gone done with each few blocks found. The find per block doesnt go down and the total hasing power is generally around 200 -210 TH so why is my share decreasing?

contract_payment    Jan. 7, 2014, 5:30 a.m.    0.005843823

contract_payment    Jan. 20, 2014, 4 a.m.    0.005436638

contract_payment    Feb. 1, 2014, 10:30 a.m.    0.005345283


So the hashrate is practically the same and the value per block found is but there's clearly a diminishing return- why?