Stats are clear. The older you are, the later you left full time education, the more middle class you are, the more likely you are to start bf.
This is not inevitable and predictable though.
Variations appear according to your ethnic group, and whether your friends and family bf, and indeed where you live.
A 30 year old married or co habiting graduate in a professional job is more likely than a 16 year old single mother with zero gcses to bf.
Yet there are plenty of individuals of both types who challenge that and do the opposite of what they are more likely to do.
And If the 30 year old lives in London she is more likely to bf than if she lives in Northern Ireland. Even if all her other demographic factors are identical.
Virtually all mothers of Chinese ethnicity bf, no matter what age and class etc.
When I say bf, I mean start to bf.
There is a drop off among all groups.