Traditional survey data collected and economic analysis by use of data are mostly annual sequence, seasonal factors, also need to seasonal adjustment.

时间序列是指在规定的时间间隔内，对经济活动进行连续测算而形成的数据。

youdao

It does not, however, appear that the seasonal adjustment scheme takes into account the fact that the most seasonal part of the economy is also the part that is much smaller than it was at the time that the seasonal adjustment factors were set.

FORBES: Seasonally Adjustment Distorts Figures