While the poor US GDP growth figure in 2015Q1 can be attributed to several transitory economic factors, problems with the seasonal adjustment of the data appear to have played a major role as well.
Although the Bureau of Economic Analysis (BEA) presents GDP as 'seasonally adjusted', the time series still exhibits seasonal variation, with a downward bias in first quarter GDP growth. In fact, once this 'residual seasonality' is removed, we may very well see a positive GDP growth figure for Q1. The BEA intends to address this issue in the annual revision on July 30.
"Our application of X-12 ARIMA to the GDP time series suggests 1.25% GDP growth in Q1." estimates Rabobank
