According to a study by Brian Burke of the Advanced NFL Stats website, the field goal accuracy of placekickers between 1974 and the beginning of this season went from 60.6 percent to 84.5 percent – this despite kicking from farther away on average. This is partly just a matter of evolutionary development, including better and better soccer-style kickers.
In the early days of the Super Bowl, there were still kickers (sometimes combo kickers/punters) who kicked the ball with their toes and not their insteps.
Other things that have contributed to greater accuracy have been consistent artificial-turf fields, climate-controlled (windless) domed stadiums, and hash marks that were moved closer to the center of the field in 1972, thus eliminating sharply angled kicks.
