Don't know if this makes any more sense Payscale but in an oversimplistic way the way ROR was explained to me is:
The ROR is the growth for the selected time period divided by the average amount invested during the period.
So if you start with $0 and contribute $1,000 per month for 10 months and end up with $11,000 the ROR is calculated as follows:
The approximate average amount invested is $5,000 assuming no pay increase etcetera and the growth is $1,000 then the ROR is 20 % or thereabouts.
Before you ask, negative RORs are calculated the same way but look better as a percentage as a discount looks smaller than a mark up.
