[bertili]

Here is a puzzle:

Investors in bonds look for a percentage growth, year over year. That's an exponential. A linear growth would be non-investable in the longer run.

From the other side, the US debt is quite linear on a log scale, so also exponential. That suddenly looks scary. But that is really to be expected? Exponential is the natural curve. If it wasn't exponential it would disappear, year over year.

[franktankbank]

Why the assumption that things are all exponential?

[bertili]

I don’t have the answers but we have a system where, if you loan out money we expect a return that is a percentage of the amount of the loan, rather than say a flat loan fee.

[anon291]

Because population grows exponentially, either up or down, and money is a means of quantifying work and labor at the end of the day. Thus its value rises in the same way

Put another way, there is no number of children per couple C such that a population initially composed of N individuals will always add X>1 number of children per year in perpetuity.

If every person has one kid (or alternately, every couple two), then the growth rate is zero and the population constant. Constant population is exponential (exponent = 0).

If the number per couple is below two, then population declines exponentially. Fewer and fewer people die each year but also fewer are added. Eventually the population hits zero

If the number is more than two, then more and more are added each year