Cal. RTC § 10753.3

(a) Except as otherwise provided in subdivision (b), the market value of a trailer coach which must be moved under permit, for each registration year of its life, shall be as follows: for the first year, 85 percent of a sum equal to the middle point between the extremes of its class as established in subdivision (b) of Section 10753.2; for the second year, 70 percent of such sum; for the third year, 55 percent of such sum; for the fourth year, 45 percent of such sum; for the fifth year, 40 percent of such sum; for the sixth year, 35 percent of such sum; for the seventh year, 30 percent of such sum; for the eighth year, 25 percent of such sum; for the ninth year, 24 percent of such sum; for the 10th year, 23 percent of such sum; for the 11th year, 22 percent of such sum; for the 12th year, 21 percent of such sum; for the 13th year, 20 percent of such sum; for the 14th year, 19 percent of such sum; for the 15th year, 18 percent of such sum; for the 16th year, 17 percent of such sum; for the 17th year, 16 percent of such sum; for the 18th year and each succeeding year, 15 percent of such sum.

(b) For the purposes of this section, the market value of vehicles which have been previously registered and which, because they are being converted to year-round registration, become subject to registration twice during the 1976 calendar year, shall be deemed to be the same throughout the 1976 calendar year and shall not change until the registration subsequently expires.