US PMI/ISM stable in November

 The usual preamble applies, about variability and estimates:

Most economic time series, in all countries, are based on sample surveys.  A group of respondents is asked  questions about the state of their business.  Because it would be prohibitively expensive to ask everybody, only a small percentage of the total is asked what is happening or what happened over the time period.  The statisticians then estimate what their small sample of actors in a sector means for the whole sector.  This introduces random errors into the data.  In addition, just like waves and ripples on the sea, there are random fluctuations in the actual economy, not just in our measurement of it. 

There are two ways to get round these issues.  The first is to 'extreme-adjust' an individual time series.  This technique measures the random error of each individual observation of the time series by comparing it with a smoothed trend (usually some version of a Henderson curve) and if an individual error term of an observation is more than 2.5 standard deviations away from the average of over, say, the last five years, that observation of the time series is replaced with the value of the moving average.  This technique removes "spikes" in the data caused by bad weather, strikes, or simple mismeasurement.

The other way is to use different surveys.  For example, retail sales data come from surveys of shops (online and brick and mortar).  Industrial production comes from surveys of factories.  If you take an average of these two time series drawn from completely different samples, you reduce the random error, and get a clearer picture of what is happening in the economy.

There are two national opinion surveys in the United States, as well as several regional surveys.  The two national opinion surveys are produced by different bodies, using different samples.  The oldest is the ISM survey, produced by the Institute of Supply Management (previously the 'National Association of Purchasing Managers', or NAPM.)  Initially the survey just covered manufacturing, but about 20 years ago, the service sector was added.  The other is produced by IHS Markit, and is called the PMI, or Purchasing Managers Index. 

Source: Mixed signals from the US

(Also, when the time series isn't seasonally adjusted, I do my own adjustment.  I do my own extreme adjustment too, both using programs I wrote.)

The signals aren't that mixed this time, but still there were slight differences in the November data―the ISM  went up a little, the PMI down.  Conclusion: no change from October, though the longer-term trend is gently down.