How much is a championship goal worth in the premiership?

We all know it’s harder to score goals in the premiership than in the championship and the reason is that the quality of competition increases as you prgoress up the leagues. I’m looking to try and put a value on roughly how much a goal in the championship is worth in the premiership (ie if a team scores x goals in the championship how many would we expect them to score in the premiership).

To do this I’ve taken the teams that are promoted to/relegated from the premiership and looked at how they perform in consecutive years. The sample size is pretty large (almost 5000 games) so the results should be pretty representative.

First I’ll look at teams that were relegated from the premiership in ‘year 1’ and consequently spent ‘year 2’ in the championship

 Year League Games Goals scored Goals per game ‘Year 1’ Premiership 1026 942 0.924 ‘Year 2’ Championship 1242 1791 1.442

So to calculate how much a goal scored in the championship is worth in the premiership:

Goals for per game (premiership)/Goals for per game (championship) = 0.924/1.442 = 0.641

How about the other way around, teams that are promoted in ‘year 1’ and playing in the premiership in ‘year 2’

 Year League Games Goals scored Goals per game ‘Year 1’ Championship 1242 2053 1.653 ‘Year 2’ Premiership 1026 1067 1.040

Goals for per game (premiership)/Goals for per game (championship) = 1.040/1.653 = 0.629

The results match very well and I’m going to estimate that a goal in the championship is worth ~0.635 goals in the premiership. By following the same process for goals conceded and I got values of 0.660 and 0.615 for relegation and promotion which back up the above results as they average to ~0.635 although the spread is much wider.

I’m aware this isn’t a perfect representation. Teams buy players as they are promoted and sell them when they are relegated so it isn’t exactly the same team playing both seasons. However the numbers are almost a perfect match so I think it’s a good model to use.

I also think this will be an applicable estimation for players although that’s something I’ll look at more closely in the future. I’m also going to do equivalencies for league 1 and league 2 to build up an idea of the relative strengths of the different leagues.