Recognizing Trends and Seasons in Excel Sales Forecasting
Baselines are often stationary: They tend to stay centered around an average value, even though they don't stick right to that average.
There’s no clear trend in this baseline. It sticks close to home.
This baseline has trend. It wanders some, but you can see that the direction is generally up.
Baselines also often move up or down — the sales figures for a product generally rise or drop with some fluctuation in the direction, but overall you can see what’s happening. These are baselines that have trend. You can see a baseline with an upward trend in the figure.
There are also baselines with seasonality.
These baselines tend to move up and down regularly over time, usually in ways that correspond to seasons. Sales of fruit rise in the spring and summer, and drop back down in the fall and winter (unless you live in the southern hemisphere).
The figure shows a baseline of seasonal sales. The size of the season’s effect on sales varies, but it’s there quarter after quarter.