What is the chemistry that ultimately leads to marriage?
Astrologers believe we can measure strong compatibility between two people by comparing their birth charts.
Carl Jung conducted one of the rare statistical studies on this topic. Not many people realize Jung was a serious student of astrology. This summary of Jung's detailed study is provided in Roots of Consciousness:
"In an analysis of 483 pairs of charts from married couples chosen at random, Jung found a perponderance of aspects that woud signify such a relationship. Most notably the moon of the woman was found to be in conjunction with either the sun, the moon, or the ascendant of her husband. A control group of over 32,000 unmarried pairs of charts did not show these aspects. Statistical analysis indicated the results obtained could have happened by chance only one time in ten thousand."
Link here for further info on astrological compatibility.
Update on January 31st, 2005:
I've just read that Carl Jung's astrological study was not as completely statistically rigorous as it could have been. For an explanation of this, see the August 8th, 2004 entry at the very interesting 0.divinorum blog.