Oldest Siblings have less Chance in Setting World Records?

Has it occurred to you that none of the recent 100m WR for men were the first born sibling?

From the book The Talent Code: Greatness Isn’t Born. It’s Grown. Here’s How, pages 115 and 116:

• Usain Bolt is the 2nd of 3 children
• Asafa Powell: 6th of 6
• Justin Gatlin: 4th of 4
• Maurice Green: 4th of 4
• Donovan Bailey: 3rd of 3
• Leroy Burrell: 4th of 5
• Carl Lewis: 3rd of 4
• Calvin Smith: 6th of 8

Even Ben Johnson was 5th of out 6 children.

Can you think of reasons why the first born (male) child would not succeed in life?  (at least, not in Track and Field World Records!)

1. socio-economic?  both parents working?  no time “early” in their work careers?
2. 1st born (male) child has career pressure? off to work first, military, college or priesthood? (hey, I live in Rome now)
3. 1st born child has financial pressure in low income families?
4. younger siblings have a better sport support system in place?
5. younger siblings have older sibling as role models?
6. younger siblings are mentally tougher being teased by their older siblings?

Or is it simply a bad sample pool and merely a coincidence?

It’s certainly an interesting point of discussion!

For the record, I am 4th out of 5 children.

The Talent Code: Greatness Isn’t Born. It’s Grown. Here’s How