They can indicate where the market is going to open, but they're not a crystal ball.
Was it a predictable event? Then Wall Street's reaction might already be "priced in."
"It's really a measure, I think, of worker confidence in the economy," said Tara Sinclair of George Washington University.
If you want to know what's going on in this economy, the bond market is a pretty good place to start.
Consumer spending accounts for about 70% of gross domestic product.