Immediate Annuities

I want to take an immediate annuity, however when I retired last year the payouts were higher than they are now. I found an annuity after 7mos that will pay me what I wanted last year..it is an immediate fixed annuity. My concern is if I annuitize now what are the chances or what makes annuity payouts go up & down? If the market gets better will payouts go higher or lower? I need money, but I would wait for the highest payout. I know your age is accountable, but now I am 1 year older & the payouts have & continue to go down than from 2quarter 2009. Thank you.