N.Y. Comp. Codes R. & Regs. tit. 11, § 166-1.6 – Annual rate formulas.

(a) RETURN ON NETWORTH_NY= INCOME_NY/SURPLUS_NY− (.5 × INCOME_NY)
(b) INCOME_NY=
(UNDERWRITING GAIN RATIO*_NY× EARNED PREMIUM_CTY)
+ INVESTMENT GAIN_CTY
− DIVIDENDS TO POLICYHOLDERS_CTY
− FEDERAL TAX_CTY
− ADJUSTED FEDERAL TAX
(c) ADJUSTED FEDERAL TAX =
(.46 × UNDERWRITNG GAIN RATIO*_NY× EARNED PREMIUM_CTY)
− (.46) × (UNDERWRITING GAIN_CTY)
(d) SURPLUS_NY= SURPLUS_CTY
+ (1 − .46) × (UNDERWRITING GAIN RATIO*_NY× EARNED PREMIUM_CTY)
− (.46) × (UNDERWRITING GAIN_CTY)
(e) In the formulas above:
1. (1) NY = New York (from N.Y. Ins. Dept. Loss and Expense Ratios)
2. (2) CTY = Countrywide All Lines (from Best's Aggregates and Averages)
3. (3) .46 = Assumed Federal tax rate
  * for Automobile (Motor Vehicle) Insurance only.
(f) See section 166-2.6 of this Part for discussion of this section.

The formulas which shall be used to calculate the tindustrywide annual rate of return on motor vehicle insurance written in New York for the period 1974-1983 follow: