It doesn't seem like you have enough data points to split your regression like that, based on the number of points in each graph. You appear to have less than 10 points per time period. The typical rule of thumb is 25 data points per variable so I wouldn't be testing a ton of models here either. They all appear linear so I'm not sure if there's even any value in testing the quadratic but its easy enough to do in your model statement. Add a By statement to your desired regression procedure, for this, PROC REG or GLM may be fine, you don't have enough data for anything more complex.
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