Hi @alcfashion
It’s a good question!
I couldn’t collect the data myself, because it has been being collected for the past 20 years (I would have had to have started collecting when I was 7 years old if I had collected it all!).
I use data from what is called a ‘birth cohort’, it’s being used by hundreds of scientists to research loads of different questions, and a number of people are employed to collect the data. It’s a great system.
Let me know if you’d like any more information! 🙂
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