I'm curious to understand the reasoning behind making XRP a fixed money supply. From my own understanding, it seems that monetary policy needs to be somewhat elastic in order to keep inflation in check. From what I have read, Ripples are limited to a supply of 100 billion. Right now that seems like a huge number, but as we've seen with Bitcoin there is a lot of room for digital currency to grow. Where did the 100 billion number come from?
It actually came mostly from technical requirements of the software design. We wanted to use 64-bit integers for XRP balances and we wanted XRP to be divided into at least millionths. There are various reasons to limit the range to less such as being able to sum XRP balances inside a 64-bit integer without having to check for overflow. We also wanted a round number that was easy to remember. Otherwise, the larger the better made sense so that you could have as many units of currency as possible to reduce the chances that a change would be needed to increase divisibility.