[4] This price volatility appears to occur in cycles and is caused by a myriad of factors.
In this case the rate is derived as follows: A trend was calculated for the resulting discounted price curve using the method of "least squares".
The discount rate was then derived by seeking the goal of a trend of 1, i.e. flat.
Using this as a baseline rate, the normalized price curves were calculated for the other commodities.
Oil and gold had similar normalization rates, but Stocks tended to beat this trend, while rents tended to lose against this trend in the period observed.