I'm not entirely sure if I've asked the right question, but does anyone know why certain symbols (I assume they are the symbols) change on NASDAQ?
In particular I'm wanting to keep a track of the Natural Gas price. It's current code is NGH16.NYM and I've been following it here http://finance.yahoo.com/q?s=NGH16.NYM&ql=0
However last month the code was NGG16.NYM and had this URL http://finance.yahoo.com/q?s=NGG16.NYM&ql=0
I've been struggling with this for a while now, and at first thought it was an incremental code. That pattern didn't seem to stick.
Any ideas? And any idea if I can predict the next ones?