The Institute for Supply Management said its May manufacturing index improved to 55.4 from 54.9 a month earlier, the Tempe, Arizona-based group said in a second correction on the data.
Group survey Chairman Bradley Holcomb said earlier in telephone and Bloomberg Radio interviews that incorrect seasonal adjustments were applied to the May figures.
Holcomb had initially said the corrected reading was 56.0. The group first reported the gauge fell to 53.2 from 54.9 in April.
The median forecast in a Bloomberg News survey of 82 economists was 55.5, with estimates ranging from 54 to 57.
Manufacturing accounts for about 12% of the economy. The ISM’s factory gauge averaged 53.9 for 2013.