Page 114 of "The Winning Horseplayer" 1983.

"The projection method produces extremely accurate figures, but it also causes one subtle problem - a problem I had once thought was due to my personal errors until I found that it troubles almost everyone that makes figures this way. When handicappers make their projections, they tend not to anticipate enough improvement for horses who win races. If the projections are lower than they should be, the resultant figures are lower than they should be. And after a while the handicapper will notice that all his figures seem to be shrinking.......When I first encountered this problem my figures were shrinking so fast that I could barely compare recent races to ones that had been run two months earlier. Fortunately, the remedy for this problem is a simple one. At the end of each month, I review all the results and compare the figure of each race with the par figure for that class. If I find that the races have been run, on the average, one point slower than par, I will retroactively add one point to all my variants and figures for the month". 1983