“(2) The formula is- MFR = LR(1 + ((x-y)/y + P) Where: MFR is the maximum fair rent; LR is the amount of the existing registered rent for the dwelling-house; x is the published index in the month immediately preceding the month in which the determination of a fair rent is made under part IV; y is the published index for the month in which the rent was last registered under part IV before the date of the application of registration of a new rent; and P is 0.0075 for the first application for rent registration of the dwelling-house after this Order comes into force and 0.005 for every subsequent application. … (8) For the purposes of this article: … (c) “index” means the monthly United Kingdom Index of Retail Prices (for all items) published by the Office for National Statistics.”
“A numerical scale showing the relative changes in the cost of living, wages, etc, with reference to some predetermined base level.”
“ … When considering how we should approach the application of the order, we were of the opinion that we had two options. The first option was to use the data published and therefore adopt the figure of 375.6 for May 1985. The second alternative was to interpolate the data to calculate a figure that could be adopted into the formula. Having carefully considered the wording of the Order, it clearly states that the figure to be used in the y part of the formula should be “the published index for the month in which the rent was last registered under Part IV before the date of the application for registration of a new rent”
“The second alternative was to interpolate the data to calculate a figure that could be adopted into the formula”
“… to fill in as an intermediate term of a series (maths)”