Goal Efficiency Rating = Goals kicked by player in home-and-away season / [Average goals per match for home-and-away season (all teams) * Number of matches in home-and-away season]
Hence, this adjusts for players in earlier seasons having less games in which to score goals, and that scoring in earlier seasons was less common. (Based on the GER, I said that Gordon Coventry's 1929 was the most impressive.)
One point I made in that post was that the drop in reliance on one player (generally the full-forward) to kick goals seems to have been happening for a while, but it hadn't really been noticed due to the higher scoring. Well, a year on, it occured to me to show this graphically.
The graph above shows that the GER was rising from 1897 and peaked in about the 1930s/40s. Since then it's been on a trend downwards (though of course spiking up when great goalkickers like John Coleman and Peter Hudson were playing). But because scoring reached its peak in the 1980s/90s, and there were more games, players like Jason Dunstall, Tony Lockett, and Gary Ablett routinely beat the goalkicking totals of forwards past*, although those players were also outstanding for their era. Now the reliance on a primary goalkicker looks to be as low as it's ever been. The game has changed, and at this rate, Coventry's feat of scoring 30 per cent of an average match's goals looks like it will take a long time beating.
*Scoring spiked up again in the year Buddy Franklin kicked 102 (in 2008).