The effect of stratification into FIT and NOT-FIT years (see text) on the relationship between Nino 1+2 sea-surface temperature anomalies, and rainfall over the West Sahel. Linear fit lines for FIT years (squares) and NOT-FIT years (circles) are solid and dotted, respectively. The reduction of variance (ROV) for the entire sample is only 17%, statistically significant but small. When the correlations are calculated for only the FIT years, ROV=57%, large and statistically significant. The ROV for the NOT-FIT years is neglible (<2%).