Relative popularity of birthstones?

Is there any marketing research that has shown the relative
popularity of birthstones? By this I mean that it would seem very
likely that some birthstones are going to be more popular than
others and it would seem likely that people born in July are more
likely to be enthusiastic about rubies than people born in June, who
are probably a lot less likely to be excited about Alexandrite.
Nothing against Alexanderite. But genuine stones do not seem to be
nearly as available or affordable, compared to say, amethyst, which
is very popular as a birthstone. How many diamonds are sold as
birthstones? It would seem that most diamond purchases are not made
because it is the birthstone for April. Is anyone keeping track? Are
opals more popular than pink tormaline for October birthstones? My
daughter has informed me that she expects an opal for her birthday in
two weeks.

The promotion of birthstones is a stroke of marketing genius. We
jewelers can say, “Don’t worry that you don’t have a favorite
gemstone. It has been chosen for you.” But how well is it working
with genuine stones? Surely this has been worthy of some kind of
marketing study.

Stephen Walker