by Calculated Risk on 3/28/2008 01:47:00 PM

The BEA releases Personal Consumption Expenditures monthly (as part of the Personal Income and Outlays report) and quarterly, as part of the GDP report (also released separately quarterly).

You can use the monthly series to exactly calculate the quarterly change in PCE. The quarterly change is not calculated as the change from the last month of one quarter to the last month of the next (several people have asked me about this). Instead, you have to average all three months of a quarter, and then take the change from the average of the three months of the preceding quarter.

So, for Q1, you would average PCE for January, February, and March, then divide by the average for October, November and December. Of course you need to take this to the fourth power (for the annual rate) and subtract one.

The March data isn't released until after the advance Q1 GDP report. But we can use the change from October to January, and the change from November to February (the Two Month Estimate) to approximate PCE growth for Q1.

Click on graph for larger image.

This graph shows the two month estimate versus the actual change in real PCE. The correlation is high (0.92).

The two month estimate suggests real PCE growth in Q2 will be under 1% - but still positive.

In general the two month estimate is pretty accurate. Sometimes the growth rate for the third month of a quarter is substantially stronger or weaker than the first two months. As an example, in Q3 2005, PCE growth was strong for the first two months, but slumped in September because of hurricane Katrina. So the two month estimate was too high.

And the following quarter (Q4 2005), the two month estimate was too low. The first two months of Q4 were negatively impacted by the hurricanes, but real PCE growth was strong in December.

Looking at the data, real PCE has been essentially flat for four straight months. Based on various economic reports, I'd expect March to be even weaker. This suggests that real PCE in Q1 will still be positive, but somewhat below the two month estimate of 1%.

In Q4, real PCE increased 2.3%, but real GDP only increased 0.6%. With real PCE below 1% in Q1, I'd expect a negative real GDP report for Q1. This is very similar to how the last consumer led recession started in 1990.