In this paper we follow the recent empirical literature that has specified reduced-form models for price setting that are closely tied to (S, s)-pricing rules. Our contribution to the literature is twofold. First, we propose an estimator that relaxes distributional assumptions on the unobserved heterogeneity. Second, we use the estimator to examine asymmetries in price-setting behavior. Using micro price data underlying the Swiss CPI we find that a substantial share of asymmetries in the frequency of price changes can be traced back to a rising aggregate price level. We show that asymmetries would be reduced substantially in the absence of aggregate inflation.