Comparing wealth across different places and eras is a fairly futile task.

How does one define wealth? An intuitive approach is to compare net worth by converting everything into a common currency. Performing this calculation in the present is simple (just apply the prevailing exchange rate) but how do you perform these calculations across different time periods? This becomes trickier.

One approach is to allow for differences in inflation between the two periods, i.e. express past wealth in today’s dollars. This approach might even allow for differences in purchasing power, i.e. to compare costs of a comparable basket of goods across periods / countries. The method is fine for relatively short differences in time but it loses meaning as time periods stretch out. Why?

Firstly, because the calculation used to inflate currency is exponential so very small differences in inflation assumptions can have a huge impact over hundreds / thousands of years (e.g. $1 over 500 years at 2.0% inflation is $20,000, at 2.1% is $32,500, and at 3% is $262,000). Economic historians are intelligent creatures but they lack the data to reliably estimate a complete time series of inflation and exchange rates (in fact, estimating inflation from quarter to quarter in the present is a pretty major undertaking!).

And secondly, differences emerge that aren’t accounted for by inflation alone. For example, a unit of wealth in first century Rome will buy a very different basket of goods / services to a unit of wealth in 18th century South Africa so a comparison between these units even if it were known is quantitatively meaningless (note: the bundle of goods used to estimate inflation today changes from time to time to reflect developing changes in goods / services).

So, yeah, it’s very likely you’re going to encounter all sorts of different opinions about the richest person in history depending on whatever spurious method / assumptions happen to be used to perform the comparison.