It actually doesn't really matter since all list three of them list their interest rates by APY (annual percent _yield_). So, when Emmigrant says their rate is 3.25% annually they've already accounted for how they compound the interest. Same with the other two. I suppose it makes a tiny bit of difference if you're moving money around a lot but probably not enough to bother thinking about.
The actual formula is (I'm doing this by memory, so sorry if I'm wrong . . .somebody will correct me.)
New balance = Old balance * (1+ (annual interest rate/number of times per year compounded)) to the exponent of ((annual interest rate/number of times per year compounded) * number of number of times compounded))
However, since we only know ING's (Emmigrant, etc.) APY we'd have to calculate the true annual rate before we could actually use the formula. Somebody might get that ambitious, but I hear a baby waking up, so it's not going to be me . . .at least not right now
