I have a dataset that includes real world data (not experimental or survey data) for a set of countries year by year for 40 years. The data was collected by entities such as the World Bank and United Nations. We want to see how well this data predicts things like GDP. In the OLS case, R2=0.47 but the residuals are not anything close to normal. And bunch up on one side of the plot and have a strong linear trend as well--not random. Curve fitting showed that a cubic distribution worked best. (A little effort yielded a lot of result.) R2 on the cubic model was .59. SPSS only gives unstandardized residuals for nonlinear regression (Maybe because standardized doesn't make sense?) Plotting the unstandardized residuals is still not normal. Shapiro-Wilk is still

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