bbtomato

stingreye Wrote:
-------------------------------------------------------
> You start with 0
> You borrow 1000
> You earn up to 1009.8155
> You pay back 1004.9629
> Profit 4.8526
>
> So if you tried to calculate a HPR its
> Ending - Begining / begining
>
> (4.8526-0)/0
> It approximates infinity.

It's not correct to view it like that. Here an investment of 1000 yen turned into 1004.9629 yen, a return of 0.496%. Whether those 1000 yen were yours or your sister's is immaterial. No such thing as infinite return.