Predicting Future Rent

[Eric L.]

The latest thread on calculating appreciation over time got me thinking. What factors go into calculating rent prices over time?

It seems that we always try to calculate the value of our property in X amount of years, but we rarely try to calculate rent in X years. Graphs for housing prices vs inflation and historic price increases are readily available for calculating house values, but I rarely see information like this for rent prices.

Exactly how do you go about trying to predict rent changes?