I have always thought picking a start date, end date decades later, to compare investing results highly stupid. I have never seen someone invest all the money they will ever invest one one day in their 20s or 30s only to come back 30 years later to see how they did. James' suggestion to do a monte carlo simulation just moves the needle from highly stupid to very stupid.
I think you might not understand what the Monte Carlo simulations do.
We never know what conditions will exist at the time one starts, and ends, their investment adventure. The MC will play out many possible scenarios based on historical market behaviour, and shows you the
range of possible outcomes. This is useful when considering withdrawal strategies, like living off your portfolio... this is what
@MrBlackhill gave an example of. The MC simulation is very appropriate for assessing that situation.
At the end of the day I think the dominant reason for financial success or not is an individual's behaviour and habits.
I agree that the investor's behaviour and habits are extremely important. But they cannot overrule the random and unpredictable nature of markets.
An investor can do all the right things, make all the smartest decisions and have optimal behaviour ... and can
still fall short of the historical average market performance. This is due to the random or unpredictable nature of the market.