Limitations of moving averages
We used moving averages to smooth out the seasonal variation in a time series, but this method has serious limitations.
Tourist arrivals in Fiji
Estimating a common seasonal effect
For monthly data, seasonal patterns are ones that repeat in a similar way each year. A common seasonal effect for January can be estimated by averaging the amounts that January values are above their 'smoothed' values, and similarly for the other months. Negative values for the seasonal effect correspond to months where the values are, on average, lower than their smoothed values.
Tourist arrivals in Fiji