The table below compares the fifteen years immediately after the change in the All-Ireland series with the fifteen years immediately before the change. It looks at the number of different teams that qualified for a semi-final and a final. It also counts the number of different winners. In all three situations the change seems to coincide with a reduction in competition. Less teams qualified for semi-finals/finals and the 15 titles were distributed among 7 counties compared to 8 counties before the change.
Bigger HHI numbers indicate greater concentration and less competitive balance. The HHI for the All-Ireland winners for 1986 to 2000 is 1,644. It increases to 2,089 for the period 2001 to 2015. The increase in concentration also holds for the individual games played over the period. In any given year there will be three games (ignoring draws). There will be two semi-final winners and one final winner. Over a 15-year period there will be 45 winners of individual games. The HHI measure for these 45 games between 1986 and 2000 is 1,328. The HHI for 2001 to 2015 is 1,743. Again, there has been an increase in the concentration.
It is possible to be seduced by the romance of Tipperary playing in an All-Ireland semi-final for the first time in the living memory of most of us. There is a tendency in all of us to think that none of this stuff happened before. Conor McGregor seemed to believe that he was the first Irish person to grace the cover of Sports Illustrated until his slip was pointed out (here). Rather than make the leap that the new All-Ireland structure is better than the old, it might be better to send the advocates in search for the exploits of Clare in 1992 or for Leitrim in 1994.