When you contribute to your TSP account, DFAS forwards the funds on anywhere between the 1st and 4th of the month. This is between 0 and 3 days of-non interest earning stagnation! Over a year, this is a month of not earning interest. Furthermore, since your mid-month pay is about the same as your end of month pay, half of your contribution is stagnant for about 15 days! Since you have earned that money at that point, who should be gaining the interest on it? Let's look at the numbers. We will say you contribute $12000 every year to the TSP. That is $1000 each month or $500 each pay period. Because YOU are not getting the interest, the government is getting 1.9% of your money....assuming a 4% interest rate compounded twice a month. Why do we not get paid interest on the money we have set aside? The simple answer is to make two deposits per month...ON PAY DAY. Does this irritate anyone else?