The velocity of light data from four different sources are tabulated and edited to provide data sensitive enough to distinguish between a decrease in c of the size claim by Setterfield and Norman and constancy. The analysis of these values yields a tlme-dependent weighted regression model with significant fit and statistically significant trend. Data analyzed by time subintervals, distribution, accuracy and precision yielded results in support of the regression model. Attempts to determine an experimental or experimenter bias to account for this trend were unsuccessful. Some examples of physical evidence which might support Setterfield's hypothesis are discussed.
