While there is no doubting that this has been a major influence on the trends, there are other factors that have been significant over the longer term.
A number of key milestones include the move from trained Department personnel to mechanical grading in 2004 - the rock on which the Quality Payment System grid was introduced in 2009.
Contrary to the commonly held belief that grading machines were brought onto killing lines to improve the level and accuracy of service for farmers, a key driving force behind their introduction was actually a move by the Department of Agriculture to save money.
A report produced at the end of 2003 by the Department of Agriculture entitled Expenditure Review of the Beef Carcase Classification Scheme set out the criteria for a withdrawal of department staff from grading duties.
This report noted that the cost to the Department for grading services in beef plants amounted to €4.7m annually.
Trials of three different types of mechanical grading machines held by Teagasc between 1999 and 2000 showed that the best results that could be achieved were that between 94.2-97pc of carcases analysed by the machines came to within one subclass of accuracy for conformation, with the figures for accuracy in relation to fat scoring reaching only 74.4-79.6pc.
And most significantly for those better R and U grade animals was the line after the completion of the 2000 study, "Biases were again evident, particularly for conformation class, with all systems tending to underscore classes R and U."
Despite this the machines were introduced in the autumn of 2004 at a time when the percentage difference between R and O grades was 14.6pc. There were 50.9pc R verses 36.3pc for O.
In the following two years there was a very marked fall off in R grades. By the end of 2006, O grades numbered 43.5pc, with R grades on 42.9pc, there was also a fall off in U grades in those two years from 7pc in 2004 to 6.2pc by 2006.
From 2006 to the end of 2012 the percentage of R grades recovered slightly and held dominance over the Os.
However, it then gradually slipped downward until in 2013 numbers of R grading bullocks crashed to 36pc.
It wasn't all bad news though. Numbers of steers grading U or better rose steadily from a low point of 5.8pc in 2008 to reach 11.2pc in 2013. The percentage P grade bullocks had remained fairly constant from 2000-2012 varying from year to year from 5pc-6.8pc.
The traditional national balance of half dairy stock and half suckler stock going through the system was irrevocably changed with the abolition of milk quotas. By the end of 2013 dairy cow numbers surpassed those of sucklers.
As the dairy sector advanced they took full advantage of the processing sectors bonus payment system for Aberdeen Angus and Hereford breeds.
They increasingly crossed their Holstein, Friesian and Jersey cows with either breed as they cashed in on the market. However, with each successive year it became more and more difficult for those who bought them to achieve the expected grid grade bonus after fattening.
Dairy expansion has also driven the numbers of those poorer quality P grades significantly higher. They rose from 6.8pc in 2012 to a top of 14.8pc in 2018.