It's interesting to look at the one time events that have happened in the last few (or several) generations. The destruction of farming/agriculture as the primary source of employment and the post war boom would be two big ones.
I think the change in agriculture is interesting here because the decision making process for the child of a (relatively poor) farmer wouldn't have been very involved, they would be quite likely to do what they knew. There would also probably be quite some pressure on them to get to it.
The post war boom is interesting because there were substantial opportunities for every single 18 year old that went looking for them. That's probably still reasonably true today, but the opportunities are at least riskier (in a life trajectory sense) than getting a good paying job at a mill or factory.
