The inpatient hospital deductible for 1987 shall be $520. The inpatient hospital deductible for any succeeding year shall be an amount equal to the inpatient hospital deductible for the preceding calendar year, changed by the Secretary’s best estimate of the payment-weighted average of the applicable percentage increases (as defined in
section 1395ww(b)(3)(B) of this title) which are applied under
section 1395ww(d)(3)(A) of this title for discharges in the fiscal year that begins on October 1 of such preceding calendar year, and adjusted to reflect changes in real case mix (determined on the basis of the most recent case mix data available). Any amount determined under the preceding sentence which is not a multiple of $4 shall be rounded to the nearest multiple of $4 (or, if it is midway between two multiples of $4, to the next higher multiple of $4).