One thing that I find fascinating is the variablility of future estimates of portfolio evolution, where you randomly select annual returns from historical data and ... >And see what happens, compared to what actually happened, right? Exactly!   For example Here the green graph is the actual portfolio evolution, starting with $1.00 in 1970 and continuing for 30 years. The red curves are various results of randomly selecting a year (from 1970 to 2000) then applying the annual returns for that year a total of 30 times ... then repeating to get another chart.. >Uh ... what portfolio? Just the S&P500 or maybe ... I can't remember what I used for that animated chart, but there's a spreadsheet where you can play:

You choose a couple of assets (by moving the sliders: for example S&P500 + Gov. Long Bonds)
and the allocations and some withdrawal rate (in case you're withdrawing) and some inflation rate which is applied to the withdrawals.

Every time you click on a button you get Another Random Selection of yearly returns ... so you can compare with an actual $1 portfolio.

There's also another button which, when pressed, will do 100 of these random 30-year selections and tell you how many survived.

>And I click on the picture top download the spreadsheet?
Yes, as usual.