[Harmless Teddy Bear]

There was no interest earned—the government does not invest your contributions.

Actually they do. They loan it to the general fund. In other words, savings bonds.

That is why I used that method of calculating the return.

[dinodino]

You are being disingenuous. The bonds are indeed purchased, but the proceeds do NOT go to Social Security Recipients—instead, they are returned to the general operating budget of the Federal Government. There is no “trust fund.”