A money judgment of a court of this state on a contract that provides for interest or time price differential earns postjudgment interest at a rate equal to the lesser of:

1. (1) the rate specified in the contract, which may be a variable rate; or
2. (2) 18 percent a year.

Amended by Acts 1999, 76th Leg., ch. 62, Sec. 7.18(a), eff. Sept. 1, 1999.