Economic growth surged in the second quarter this year. The only question is, by how much?

Predicting

this Friday's GDP report is trickier than usual. First, it's the initial report for the quarter. Second, we have to wait until Thursday for key data on exports and imports, which is particularly important because the trade sector looks to have had an unusually large influence on second quarter growth. And third, this is the release each year where the government goes back several years and makes revisions to its methods and calculations.

Over recent years, GDP releases have suffered from problems with "seasonality." For example, over the past eight years, real GDP has grown at a 2.2% annual rate. But the average annualized growth rate in the first quarter each year has been 1.3%, while the second quarter has averaged 2.8%. The government is supposed to apply seasonal adjustments to make sure normal winter weather doesn't artificially drive down GDP growth, but apparently those adjustments haven't been working.

So what happens if the government fixes this problem, resulting in upward revisions to Q1 growth rates and slower growth rates in Q2? We have no way of knowing if the government plans to tweak their methodology and, if so, by how much. As a result, our forecast faces atypical risks.

All that said – and keeping in mind that we might make adjustments when we get Thursday's data on durable goods, inventories, and trade – our forecast for real GDP growth in Q2 stands at 4.8%. If so, and assuming no net revisions to recent quarters, real GDP growth would be at a 3.4% annual rate so far this year and 3.2% in the past year.

Here's how we get to 4.8%: