I agree with a lot of what you say, blob, and I do think there is a 'big fish in a small sea' problem in the UK which all comes unstuck later on.
But I don't agree with: "top juniors (~10-15 and under) mostly make top 50 at worst."
I think it's more true the other way round - i.e. top 50 players were often/usually top 10 juniors.
But there is a large number of top 10-15 juniors who never make the top 50. And there has to be, because the list of top 15 juniors completely changes every 1 to 2 years (due to age). But the top 50 adults is far more stable, players can be there for 15 years. So there simply isn't room for every top 15 junior to get into the top 50 adults.
If you take the top 10 juniors at year-end, 10 years ago (i.e. they should now all have reached their primes), you have:
It's a list of tennis 'nobodies'. And the other years are the same. There's always a couple of high flyers (Dimitrov was 15th in the list for the year above). Some years there's more than others. But the majority of the top 15 never make the grade because, as said, there's just way too many of the junior top 50s to squeeze into adult top 50s. So I don't think the UK are worse here, it's just the focus should not be on junior rankings.
Interesting points. I also wonder whether a good all round game is enough to get you a solid ranking in juniors, whereas in seniors you need something more - great athleticism, a fantastic serve, a spectacular forehand. Just something that differentiates you and is difficult for your opponent to combat.
On the serve though, particularly on the women's side, I feel it's underdeveloped. Many of our players, Tara, Laura, even Heather and Naomi seem to break down when under pressure.
On the mens side, there has been some research into this generally. e.g. www.tennisicoach.com/media/114083/114083.pdf (pp. 11-13)
That's not specific to a country comparison, or the womens side, which is the point I was making really; Katy having been the inception.
The evidence CD produces, shows a mens picture, and it would be interesting to look on the womens side for the variation, and for a few different years in order to establish some benchmark. To which end, time permitting, I may cursorily attend later today (I like this sentence, with it's 19th century structure!). It would help if the historical Junior rankings were readily available.
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Data I post, opinions I offer, 'facts' I assert, are almost certainly all stupidly wrong.
You're right, blob, it was Katy who started this off so it's the women's side that's more pertinent to the discussion (although the boys is important too overall of course). But I don't think the women's side is very much different, blob, although it's true that girls' junior results do tend to mirror adult results better, partly because their physique changes less from age 17 onwards.
But you have exactly the same mathematical impossibility problem.
So, taking the same year, as comparison, the top 10 girls - with adult CHs - are:
The Junior rankings can be very flattering to our girls. At present, for example, Ms Appleton has a ranking based on her best 12 results from 32 (singles and doubles combined); but still trails several players above her, based on their best 12 results from 8.
It seems likely to me that the LTA apparatchiks are happier to find the resources to support Junior players, who must often need escorting around the globe by LTA apparatchiks, than to find ways to support the same players when they reach the lower rungs of the pro circuit; when there would be a danger that any monies received by the players would not necessarily end up in the LTA apparatchiks' pockets.
Also, the best Juniors give up early. The best Juniors in the world at present are almost certainly Bellis and Vondrousova, both still Juniors, and both WTA top 100.