Seasonal adjustment,demography, and GDP growth

Seasonal adjustment removes the predictable seasonal variation in GDP. If there is seasonal variation in factor inputs, then seasonal adjustment factors may be correlated with those inputs. This correlation can obscure statistically the importance of those inputs for GDP. This effect is apparent for the demographic composition of the labour force for Canada. Seasonal adjustment also changes the time‐series properties of GDP. Accounting for the seasonal pattern and trend change in demography suggests that the period of reduced volatility in GDP growth for Canada, the ‘Great Moderation,’ can be traced to the changing demographic structure of the labour force.