In the U.S. average inflation over the last century has been 3.2%, while the average interest rate of 10 year treasuries has been 4.9%, so you'd been able to gr

In the U.S. average inflation over the last century has been 3.2%, while the average interest rate of 10 year treasuries has been 4.9%, so you'd been able to grow your fortunes 5.4 times in real dollars, at a rate of 1.7% per year. That rate is smaller than the average rate of GDP growth, however. So, after investing your money for a century, you'd be a lot richer than in 1915, but you'd own a smaller slice of the pie.