obgyn65,
It is difficult to think of yields of life contingent immediate annuities because the annuitant could die tomorrow and the insurer makes no payments or the annuitant could live to be 110, in which case they will have made out like a bandit.
However, you can get a sense for the interest rate that the insurer pays by looking at immediate annuities not involving life contingencies. In the example that one poster shared, his SIL paid $100,000 and will receive $674 a month for 15 years. This is the same as putting $100,000 in an interest bearing savings account that pays 2.67%/annum and withdrawing $674 on the first of each month. At the end of 15 years, the account balance would be zero.
But while the annuitant receives $121,500 over the 15 years ($675 * 12 * 15 years), $100,000 is a return of their original $100,000 and the rest is interest.
A life contingent annuity is similar in that there is an interest component, but there is also a mortality factor as to how many monthly payments will be made. IMO, the best way to compare life contingent annuities is to simply compare the amount per month that you will receive for similar contracts. So if for an x year old male, one company pays $575 a month and another carrier pays $600 a month and the financialworthiness of the carriers isn't substantially different, then the $600 is the better deal.
That said, I'm not a big fan of annuities, particularly in a low interest rate environment, but an annuity may well be appropriate in your case where your SS will be low as a result of working abroad. I would probably wait for interest rates to rise, but whether you buy now or wait, it would pay to shop around.