Effective January 1, 2017 the minimum wage for all industries will be $10.50 per hour for employers with 26 more or more employees and shall remain at $10 per hour for employers with 25 or fewer employees. The minimum wage shall be adjusted on a yearly basis through 2023 according to the pre-set schedule shown above.
A 20 degree pressure angle allows for a smaller gear with less teeth before they begin to undercut making the base thinner than the pitch circle thickness of the tooth.
Just to complicate things, there are other pressure angles used in gears, 14-1/2 and 20 are just the most common, 18-1/2 and 25 are the 2 most often seen odd PAs, when designed from scratch, and engineer can use any PA he wishes.