A question from Yahoo! Answers:

What are the Bellwether issues?

Depends on the context.

In the Treasury bond market, a bellwether issue (aka benchmark issue, aka current-coupon issue, aka on-the-run issue) is the most recently auctioned issue for a given maturity.

More generally, a bellwether issue is a security whose behavior can help predict market movements. A bellwether stock goes up in the morning, and the entire market goes up in the afternoon. Note, however, that no one has conclusively proven that bellwether stocks exist…