要旨：Measuring the degree of competition in markets is essential for policy and decision makers. Commonly used structural indices (e.g., HHI) overlook the way in which firms compete, and hence their prices setting in markets. We propose a new measure: the Schedule (Temporal) Differentiation Metric, STDM, which encapsulates firms' market shares as well as the degree of overlap and substitution between their competing services. We demonstrate the STDM using aviation markets and discover a significant improvement in explaining price levels and structure. The information captured by the STDM also explains fares across fare percentiles depending on the competing airlines' business models.