ISM Manufacturing Index: A September Bounce Back into Expansion

Today the Institute for Supply Management published its monthly Manufacturing Report for September. The latest headline Purchasing Managers Index (PMI) was 51.5 percent, a partial bounce of 2.1 percent from the 3.2 percent decline the previous month. Today's headline number was above the forecast of 50.3 percent.

Here is the key analysis from the report:

"The September PMI® registered 51.5 percent, an increase of 2.1 percentage points from the August reading of 49.4 percent. The New Orders Index registered 55.1 percent, an increase of 6 percentage points from the August reading of 49.1 percent. The Production Index registered 52.8 percent, 3.2 percentage points higher than the August reading of 49.6 percent. The Employment Index registered 49.7 percent, an increase of 1.4 percentage points from the August reading of 48.3 percent. Inventories of raw materials registered 49.5 percent, an increase of 0.5 percentage point from the August reading of 49 percent. The Prices Index registered 53 percent in September, the same reading as in August, indicating higher raw materials prices for the seventh consecutive month. Manufacturing expanded in September following one month of contraction in August, with nine of the 18 industries reporting an increase in new orders in September (up from six in August), and 10 of the 18 industries reporting an increase in production in September (up from eight in August)." [source]

Here is the table of PMI components.

The ISM Manufacturing Index should be viewed with a bit of skepticism for for various reasons, which are essentially captured in a previous "Big Picture" comment on this economic indicator.

This [the ISM Manufacturing Index] is a highly overrated index. It is merely a survey of purchasing managers. It is a diffusion index, which means that it reflects the number of people saying conditions are better compared to the number saying conditions are worse. It does not weight for size of the firm, or for the degree of better/worse. It can therefore underestimate conditions if there is a great deal of strength in a few firms. The data have thus not been either a good forecasting tool or a good read on current conditions during this business cycle. It must be recognized that the index is not hard data of any kind, but simply a survey that provides broad indications of trends.

The chart below shows the Manufacturing Composite series, which stretches back to 1948. The eleven recessions during this time frame are indicated along with the index value the month before the recession starts.

ISM Manufacturing

For a diffusion index, the latest reading of 50.5 reversed a month of contraction after five consecutive months of expansion. What sort of correlation does that have with the months before the start of recessions? Check out the red dots in the chart above.

How revealing is today's 2.1 point change from last month? There are 825 monthly data points in this series. The absolute average month-to-month point change is 2.0 points, and the median change is 1.5 points.

Here is a closer look at the series beginning at the turn of the century.

Since 2000

To reiterate the assessment: "The data have thus not been either a good forecasting tool or a good read on current conditions during this business cycle." The ISM reports nevertheless offer an interesting sidebar to the ongoing economic debate.

Note: This commentary used the FRED USRECP series (Peak through the Period preceding the Trough) to highlight the recessions in the charts above. For example, the NBER dates the last cycle peak as December 2007, the trough as June 2009 and the duration as 18 months. The USRECP series thus flags December 2007 as the start of the recession and May 2009 as the last month of the recession, giving us the 18-month duration. The dot for the last recession in the charts above are thus for November 2007. The "Peak through the Period preceding the Trough" series is the one FRED uses in its monthly charts, as illustrated here.