It was good to see George and Shamu couple in Chicago. The Chinese food, at least for the 2 Chinese restaurants we sampled, is terrific and much better than that in Philly.
On my way back, I was exhausted. The flight arrived on time and uneventfully. I got on the train to center Philly and put my duffle bag on the rack. In a short moment, the conductor came. I flashed her my monthly pass, which I borrowed from my wife who is a commuter. She told me that that pass is for female only and I have to buy a ticket of $7.
I can’t help but start contemplating why the train pass distinguishes between male and female. The only reason I can think of is to prevent the sharing of a monthly pass among multiple users. I understand that issuing an ID card-like pass with a phone is probably too costly. But how effective can it be to only distinguish female and male holders by printing “F” or “M” on the pass?
The train runs fast, so does my mind.
Assume there are N females and M males. Without the rule that distinguishing between them, the total possible ways of sharing a monthly pass between two persons is:
(N+M)(N+M-1)/2
With the rule, the total possible ways of sharing a monthly pass between two persons (same-sex only) is:
(N)(N-1)/2 + (M)(M-1)/2
How effective is the rule? The percentage of reduced possible ways of sharing is:
1- [(N)(N-1)/2 + (M)(M-1)/2]/[(N+M)(N+M-1)/2]
It seems difficult to see anything. Let’s assume that N=M, which is close to reality. We can simplify it to:
N/(2N-1).
It is about 50%, when N is sufficiently large. This is not surprising. But considering there is almost no fixed costs associated with this (only monitoring costs incurred), the effectiveness is amazingly good. This is a well designed mechanism. I didn’t feel sorry for my $7.
While I just finished my thought, the train stopped at a central Philly station. I got off the train and got on the other train going to my home. It was about 10:30pm. Suddenly, I remembered I left my duffle bag on the first train. Speaking of absent-minded!! I can’t express how disappointed I was, although there were nothing important but smelly soccer jerseys in it. I was hopeful in that if the train system has such smart people to design the rule they must have a well-designed “lost and find” program.
At 11:30pm, my cell phone rang. I was told my duffle bag was in the “lost and find” office and ready to be picked up the next day.
I missed the Chinese food in Chicago but I think I like Philly a lot more.
Posted by Made In China at September 5, 2006 11:06 AM