The Fee Ration Multiple (FRM) is a technique used to measure the increased fees PoW chains will need to have to maintain their security without inflation.
FRM is expressed in multiples and is found by dividing Transaction Fee Revenue by Transaction Fees. This equation gives each chain a numerical value that represents the multiple fees needed to increase to maintain a chain’s security budget. For example, if Bitcoin miners make $10B in revenue and only $100M in fees, Bitcoin would have an FRM of 100 ($10B/$100M = 100). An FRM of 100 means that the fee revenue on Bitcoin would need to increase by 100x to maintain its security budget.
The lower the FRM, the better, as the chain will not need to increase its fees to cover its security.