To investigate this I went back over the leading goalkickers for each season and evaluated them according to a metric that, for want of a better term, I’ll call a “Goal Efficiency Rating”. The formula for this rating is as follows:
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]
Essentially to calculate the rating a player’s goal total over the season is divided by the average number of goals that would be expected to be kicked in a team’s matches over that season. For example, in 1970 Peter Hudson kicked 146 goals in the home-and-away season. The average number of goals per match that season was 24.77 and there were 22 matches, so the average number of goals that would be expected to be kicked in a given team’s matches in the 1970 season is about 545. In kicking 146 goals for the season, Peter Hudson kicked 26.80 per cent of the goals that would be expected to be kicked in a given team’s matches over that season. (Note this is different from the actual percentage of goals that Hudson kicked in Hawthorn’s matches that season.)
Using this formula, the best goalkicking season home-and-away season ever is... Gordon Coventry in 1929. Coventry kicked 118 goals when the average number of goals that would be expected to be kicked in a given team’s matches in the 1929 season was about 387 (21.55 goals per match multiplied by 18 matches). Bob Pratt’s 1934 season (where he kicked 138 in the home-and-away season, and 150 overall) comes in second, and John Coleman’s 1952 season comes in third.
Below are the ‘Goal Efficiency Ratings’ for every leading goalkicker since 1897. Leading goalkickers in the 2000s tend to be near the bottom of the table, suggesting that the modern era does indeed have the least reliance on full-forwards. In fact the 2011 Coleman Medallist, Lance Franklin, comes in at second last on the table. (Only leading goalkickers are included in the table, so for example, Peter McKenna's 1970 season goal tally isn't included.)
Some of the modern-day 100 goal seasons take a battering in these rankings, as scoring is relatively higher than it was in, say, the ‘20s or ‘30s, and more matches are played. So the drop in reliance on the full-forward to kick goals seems to have been happening for a while, but it hasn't really been noticed due to the higher scoring.
John Coleman comes in three times in the Top 10 "GER"s, while Peter Hudson and Gordon Coventry make the Top 10 twice. Again, makes you wonder what Coleman would have done if he played more than 98 games, doesn’t it?