10% inflation over 7 years will 1/2 it's worth. Rule of 70: the formula goes like this 70/percent = # of years. So if you assume inflation is 7% over the long

10% inflation over 7 years will 1/2 it's worth. Rule of 70: the formula goes like this 70/percent = # of years. So if you assume inflation is 7% over the long term then 70/7= 10 years to loose half and 20 years to keep 1/2*1/2=1/4 (lose 75%)