Ahead of the Bell: Manufacturing Index

Manufacturing activity probably increased in April for the 21st straight month, but at a slower pace than in March.

Economists forecast that the Institute for Supply Management's index of manufacturing activity will drop to 59.6 in April from 61.2 in the previous month. That would be the second straight drop, a sign the manufacturing sector is cooling off after expanding in February at the fastest rate in nearly seven years. A reading above 50 signals expansion.