Seasonal adjustment is the process of removing the seasonal fluctuation from a series. The use of this process is popular in the field of economic research, as it provides a better overview of series changes over time. A common example is the Gross Domestic Production (GDP) index, one of the main indicators of economic health. This indicator has a strong seasonal pattern, as the majority of production in most sectors is affected by seasonal events through the calendar year, such as weather (for example, the agriculture sector) or holidays (for example, the retail and airline sectors). As a result, in a calendar year, some calendar quarters (for example, the first quarter of the year) will be higher (or lower) than others.
The US GDP is a good example as, historically, the growth in the first quarter is the lowest and highest in the second quarter, due to those...
