While you are trying to work that one out, here is a supplementary: Whose record did he overtake? Greg Norman, perhaps. No, in fact it was his own.
For the last two seasons Irwin, who plays on the US Senior Tour, has been the biggest money winner on any single circuit. Last year he won $2.3m (pounds 1.4m) while Woods led the regular tour with $2.1m. Last Sunday, Irwin won the Senior Tour Championship to top the list again with $2.9m compared to Duval's $2.6m.
The strength in depth, of course, is nothing compared to the regular circuit, where 26 players passed $1m this season. But the fact that 11 seniors also broke through the seven-figure barrier shows what a remarkable sport golf is when a bunch of 50-year-olds can earn similar winnings to those in their prime.
You would think they would get fed up with all the travelling and the constant grind of tour life but, with over 40 tournaments worth over $40m, who is complaining. As Julius Boros asked: how do you retire when you have spent all your life playing golf and fishing? And don't bother with the Viagra, there have been creche facilities on the Senior tour for years.
Irwin does not just play on the tour, he dominates it. His latest win was his 20th in four years. He won nine times in 1997 and seven times this season, including the PGA Seniors' Championship and the US Senior Open. He led the tour in putting, greens in regulation, birdies per round and lowered the stroke average record to 68.59.
But who exactly is Irwin beating? His nearest challenger is Gil Morgan, who has won six times in each of the last two seasons and finished second on the money list with over $2m each time. Last Sunday, Morgan, the defending champion, went into the final round with a one- stroke lead but Irwin shot a 65 to win by five. With no one else near enough to challenge the top two it could be a great rivalry. But the outside world is showing little evidence that it cares very much. What Irwin and Morgan lack is the one thing the Golden Oldies circuit was founded on: charisma.
Irwin, at least, was a major champion. But he will be remembered for the admired but hardly thrilling achievement of hitting enough fairways and greens to win three US Opens in three different decades. Morgan won seven times in his regular career but the most exciting line in his biography is that he is a non-practising optometrist.
Arnold Palmer was the catalyst for the Senior tour in the early 80s. Arnie's Army still had eyes for only one man, he just needed a different playground. The tour reached its zenith earlier in this decade when Lee Trevino - who won a record 27 times before the "round bellies" started to flatten - Jack Nicklaus and Ray Floyd arrived on the circuit.
Nicklaus never wanted to be seen playing full time on a ceremonial circuit but, ironically, his desire to perform at the highest level helped move the Senior tour away from that image towards a highly competitive arena. It is now one where the lifespan of a senior in terms of regularly contending has shrunk to under five years.
Also falling, however, are the television ratings. "Our product is fairly bland. We all realise there's a little bit of a lull right now," one tournament director told an American magazine last year - after only one season of the Irwin-Morgan show.
"Irwin and Morgan are not real exciting to watch," said Johnny Miller. "They don't relate to the galleries like the old superstars. It's one down from having Trevino battling Nicklaus, that's for sure."
Miller, the former British and US Open champion, has only been persuaded to come down from his commentary tower for a couple of Senior events and immediately retreated when he scattered putts all over the place. The next big names to join the circuit - and that is not definite since they have already cashed in on the regular tour - are Tom Watson, Tom Kite and Lanny Wadkins.
"I will play the senior tour but I'm not sure how much," said Watson. "It might be more fun over there, seeing a lot of old friends and less pressure in a way. But what Jack Nicklaus told me is absolutely true: `Tom, these guys can really play'. It's no place to go thinking of making a half-hearted effort."
Watson will be the first of the trio to arrive but not until next September. That gives Irwin another season to clean up. "I have a lot of confidence and I'm putting well," he said. "There's no sign of weakness in my game unless I let it happen. Somewhere along the line the streak will slow down a bit. But right now, I don't intend to let it happen."Reuse content