Market Fluctuations

How to Input Possible Market Fluctuations

I assume when using Monte Carlo Planning that the Regular Assets Income on the Total Income Report shows the expected mean return for each year, taking into consideration years when historical stock returns are higher in some years and lower in others. I have not found any specific way to input times in the future when someone could guess when returns could possibly be very low, such as they were in 2008, or high, like 2017.