The weight-for-age scale could be a huge factor in deciding some of the big races at York's Ebor meeting this week, not least in Friday's Coolmore Nunthorpe Stakes.
WFA is something that is unique to horse racing as participants in no other sport compete on only notional level terms. In athletics, the sprinters in the 100 metres start in a straight line irrespective of age. In football and rugby it's 0-0.
But, because horse racing allows immature animals to race against mature ones, an allowance is needed. We race babies against adults.
So, in this week's Nunthorpe, the two-year-old Pershaada will receive a massive 27lb from the older male horses, and slightly less from the fillies and mares who get a sex allowance.
If she wins well, the concession will look like a gift. If she fails it may even have been too little.
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The outcome may depend on whether Pershaada is above or below average for her age as WFA is purely an average assessment of differences in maturity at various stages of the year.
Two-year-olds have taken advantage before. The 'pocket rocket' Lyric Fantasy sped to victory in 1992 under South African Michael Roberts and, in 2007, the Jimmy Quinn-ridden Kingsgate Native also 'ran loose' under his light weight.
Wesley Ward's strapping filly Acapulco was second to the top class Mecca's Angel in 2015.
If you think it's already complicated enough, Pershaada will not be carrying her advertised weight of eight stone, and the other runners will also be running off different weights to those you will read in the newspaper or online.
This is because jockeys get a 4lbs allowance and Silvestre De Sousa will weigh out at 8st4lb.
So why are the actual weights not published? Well, maybe it doesn't matter as the differential is the same but, still, why not publish the correct weights anyway?
Personally, I'm not sure if Pershaada is quite in the Lyric Fantasy/Kingsgate Native class and, after his back-to-form win at Goodwood, Jim Goldie's six-year-old AMERICAN AFFAIR could be the one to beat.
In Wednesday's Juddmonte International, last year's winner (as a three-year-old) Ombudsman has to concede weight-for-age to the younger French Derby and Eclipse winner CONSTITUTION RIVER who, on the latter occasion in early July, had some older rivals well behind him.
At that stage in the season, Aidan O'Brien's colt was getting 10lb in WFA. Now, just over six weeks later, the scale says he must have matured. So he gets less.
It is a complete guess whether Constitution River, who now receives only 7lb, is a 3lb better horse owing to growing maturity.
If he has made average progress, it might be just about right. But he may well have gone forward quite substantially and I doubt he has gone back.
One little conversation overheard on the French television coverage from Chantilly at the end of May has stuck with me regarding this horse.
That day, Constitution River was helped by pace-making stable companions (including the reopposing Hawk Mountain) but still achieved the near impossible by winning the Prix du Jockey Club from a very wide draw.
As Ryan Moore walked back to the weighing room, a young racegoer asked how he'd managed to win from stall 15? He replied: "Because I was riding an exceptional horse."
Moore is a serious judge and has made no secret of his regard for this colt all season.
As such, I believe he could well foil Ombudsman's attempt to join the dual Juddmonte winners Dahlia, Ezzoud and Halling in what has been billed as the clash of the season.
Ombudsman ran out an impressive winner 12 months ago from Delacroix (who had beaten him a neck in the Coral-Eclipse at Sandown previously) and it would be interesting to know whether the Coolmore 'lads' and O'Brien think Constitution River is better than Delacroix.
One suspects they do.
The two principals are both unbeaten this season and Ombudsman was again visually impressive when cutting down his rivals in the Prince Of Wales's Stakes at Royal Ascot.
His turn of foot is a lethal weapon but that form looks a bit shaky as Minnie Hauk, the runner-up, has had an in and out season and was well beaten subsequently in the King George while third-placed Daryz, last year's Arc winner, clearly performed below par and wasn't quite right when returning home.
While a surprise result can never be ruled out at York, Hawk Mountain, third in the Eclipse, and the promising Item, who bounced back from a poor run in the Derby on soft ground to win the Sky Bet York Stakes, are probably playing for places.
Weight-for-age could also be a factor in Thursday's Legends Global Yorkshire Oaks in which Kalpana will be fancied to follow up her King George triumph.
This great mare has never been better this season but she loves Ascot and has never run at York.
Moreover, taking into account official ratings and a 9lb WFA concession, the impressive Irish Oaks winner JOHANNA WALSH could prove a formidable opponent.
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