SearchInsights: Seasonal Trend analysis

Since we introduced expectation ranges for all relevant search KPIs to detect and analyze significant short-term fluctuations, it became evident that we also needed a seasonal expectation range. This would incorporate long-term data to help distinguish temporary variations from genuine long-term trends.
In essence, this approach allows us to identify and account for historical trends, preventing expected seasonal deviations from being misinterpreted as anomalies in the charts.
Implementing this was a complex challenge, but we are excited to announce the launch of the Seasonal Expected Range view for your data!
Approach:
We analyze historical data from previous years, remove extreme outliers, and smooth the data based on extracted seasonal effects. This smoothing process is performed using the Whittaker-Eilers method.
We then calculate confidence intervals and overlay them with the current year's data (the time frame of interest).
By doing so, we effectively filter out short-term outliers if they align with expected seasonal patterns. The following chart illustrates this approach using sample search CTR data.