Age-defying James Anderson still fabulous at 40

It is likely that sometime in the next couple of months, James Anderson will become the first bowler to take 400 Test wickets after turning 30. Already, he is only the second player to play 100-plus Tests after 30 - Alec Stewart was the first, with 107 - but Anderson's feat is remarkable at several levels.

For starters, he is a fast bowler, and fast bowlers aren't supposed to go on as if age is just an irrelevant number. Currently, Anderson has 389 wickets from 101 Tests after turning 30; since turning 35, he has taken 177 from 47 matches. Among fast bowlers, only Courtney Walsh, with 180 from 39, has more wickets beyond 35. Only six other fast bowlers have managed even 200 wickets after the age of 30, but Anderson is moving towards 400, and seemingly, quite effortlessly.

It isn't only the fact that he is taking wickets as frequently as he used to; his bowling average and strike rate are actually improving the older he gets. In the period from 25 to 29, he averaged 28.47; between 30 and 34, it improved to 25.45; since turning 35, his average is an incredible 21.39. And his overs per Test has dropped only marginally post 35 - from 36.4 in the previous period to 34.2.

Given this inverse relationship between his age and his bowling average, any guesses for what his average will be when he is 50?

This reverse-ageing isn't normal in sports, especially in fast bowling. Anderson's post-30 haul of 389 accounts for 59% of his career tally of 657. Among the 36 bowlers who have taken 300-plus wickets in Tests, only five have a higher percentage. And remember, Anderson isn't done yet, so by the time he hangs up his boots in the long format, the percentage will go up even higher.

At the top of this list is Sri Lanka spinner Rangana Herath, who took a scarcely believable 398 out of his career total of 433 wickets after he turned 30. Herath's was an unusual career though - he came into his own only after Muthiah Muralidaran's retirement. Among fast bowlers, Walsh, Allan Donald and Richard Hadlee are all in the mid-60s. For Anderson to go past their percentages, though, he will need to take another 125 wickets, which looks a tall order even for him.

Anderson's 177 wickets after turning 35, though, is even more impressive. Among fast bowlers with 250-plus wickets, only Walsh has a higher percentage of wickets after turning 35. The top six in this table is a stellar list of some of the best fast bowlers to ever play the game.

Anderson's improving average with age also means his ratio of post-35 to pre-35 is among the very best. Before turning 35, Anderson took 480 wickets at 28.20; since then he has averaged 21.39. That's a ratio of 1.32 between these two averages. Among the 20 bowlers who have taken 50 or more wickets before and after 35 - the length of this list itself shows how unusual this achievement is - only two have a better ratio, and both finished their careers more than 100 years ago.

With age, Anderson has also added more weapons to his arsenal and become a more complete and canny bowler. He isn't only reliant on seaming and swinging conditions to be effective - though he is still obviously more deadly when these are on offer.

A comparison of his bowling average in each country before and after turning 35 shows he has better numbers everywhere, save for India where the averages are similar. The biggest improvements, of more than 40%, are in Sri Lanka, West Indies and the UAE.

In Sri Lanka, the average has almost halved, but apart from the average, the improvement in economy rate points towards his control and mastery over his craft: since turning 35, he has conceded 2.09 runs per over in Sri Lanka (3.30 before 35), and 1.87 in the UAE (2.30 before 35). His 6 for 40 from 29 overs in Galle last year encapsulates all of those phenomenal qualities - not least his fitness - in his age-defying journey.