Adding Market Data to the Net Worth Spreadsheet

I found some historical market data on an NYU business professor’s home page. I put the first four columns on a new sheet in the Google sheets version of the net worth estimator.

I also put a sample portfolio that you could play with. It’s 70% stocks and then a mix of bonds.

Then, on the main sheet, I use the portfolio return column instead of the fixed 6% return.

Historically, a portfolio like that returned more than 6% — more like 9.5% on average. I showed three lines, one for starting in 1928, one for 1948, and one for 1958. Since I am trying to simulate 60 years, that’s about as late as I can can start. But, for planning purposes, being conservative is still a good idea in my opinion (which is worthless as I am not a financial advisor and this is not advice).

There are many things wrong with this model that I’ll address soon. The main issue is the the post-retirement spending model seems way too low. I am also using a constant inflation rate instead of historical data. Finally, wage inflation has not necessarily kept up with inflation, and certainly in down market years, we could expect wage freezes or temporary unemployment.

All of these things are a lot easier to model in python.

FIRECalc only simulates net worth after retirement, so it can do many more simulations (because of the shorter duration). Still, there are more than 40 possible scenarios in this data.

Next, I’ll add this data to the python version and try to draw more scenarios.