Where is the depth of World Junior Tennis

Very interesting ITF stat's .From the above 15 selected countries we find USA and RUSSIA leading the way with Juniors in the top 250 .USA has 51 whilst Russia 39.Spain only has 9 - 7 boys and 2 girls.Great Britain has 22 - 16 boys and 6 girls.Of course whether the junior players can transgress to the Pro senior tour is the key.All stat's are boy and girl combined. France has 14 - 13 boys and just 1 girl. Russia's Break down is 15 boys and 24 girls whilst the USA is 19 boys and 32 girls!Canada has 10 4 boys and 6 girls.Will we see a resurgence by the USA based on these numbers?New Zealand has 1 boy and 1 girl  in the top 250.