Wages differ by a few cents per hour from one Supplement to another.
Here in New England the Package Car Driver's top rate became $28.49 (which includes the first 35-cent raise) on 8/1/2008 and will rise gradually to $32.14 on 2/1/2013.
General Wage Increases occur every six months on each February 1st and August 1st in amounts of 35-cents, 37.5-cents. 42.5-cents and 47.5-cents.
When you finish your progression, you jump to the Top Rate in effect on that day.
There might be cost of living (COLA) raises as well, but only if inflation goes up significantly.