Hi Jess,
There was a guy (can't recall his name right now), who ran an analysis on Swiss court and insurance records, It was a sample size of several million individuals over a period of several years, so any result has high statistical confidence.
In terms of who got married, who got married to whom, who got divorced, and who got divorced from whom, who had more car accidents... the time of year they were born was highly significant.
You can speculate on why; daylight hours, types of food available, activity cycles etc during the last trimester of pregnancy and in the first few months after birth, is probably a pretty good area to start - the last trimester of gestation was highly found to be significant when studying those who were affected in utero and for the rest of their lives (and passed it on to their children and grand children) by the Dutch Hunger Winter...
You can speculate on the causations, the why s, but there is no speculation on the correllations, In Switzerland at least, for the periods analysed, the correllations are undisputably there.
Do I think it is down to the stars themselves?
No, the constellations in the sky at a particul;ar time of year have precessed several star signs out of phase over the three thousand or so years since the characteristics of the different personal characteristics were first written down - but the descriptions of those characteristics still hold up pretty well.
Do I think you can foretell the future from the stars?
If you can make it vague and woolly enough, some sucker will believe you were right ;)