I'm intersted in learning about how many people ride the subway each
day.  Specifically how many in each region (U.S., Europe, Asia, Japan)
and how long on average they ride on the subway (in minutes) and
perhaps, if available, what hours of the day.  Also, any demographic
data (age, sex, income, etc) would be helpful too.  If the number of
miles of subways is available too, that would be interesting.  Thanks