Fitting a piecewise function

Olympic gold-medal data in the men's heavyweight weightliftng event.
While data exists as far back as the first mordern Olympic Games in 1896, there were significant rule changes at each of the early events which make modelling difficult and inappropriate. From 1928 until 1972 there was a consistent set of rules for the competition. From 1976 until the current date, another set of rules were used. This situation lends itself to a piecewise solution with two functions modelling the data.