In fundamental analysis, increases (decreases) in the ratio of selling, general and administrative (SG&A) costs to sales (SG&A ratio) are perceived as negative (positive) signals regarding future firm performance. However, this interpretation focuses on the overall change in the SG&A ratio and ignores the underlying changes in the components of the ratio (sales and SG&A costs). Although prior research examines the changes in the SG&A ratio under some different circumstances, there is no study that examines all the ways that managers adjust costs in reaction to changes in sales. Therefore, I create six subsamples representing all possible combinations of changes in sales, SG&A costs, and the SG&A ratio and test whether changes in the SG&A ratio are informative about future earnings, analyst forecast revisions, and stock returns under these different circumstances. I find that changes in the SG&A ratio in four of my six subsamples provide information about changes in future earnings. I also find that analysts do not impound all of the information contained in the signals into their forecast revisions and in some cases investors appear to understand this fact.