Parametric insurance has made its biggest impact so far with catastrophe bonds covering large-scale risks, such as hurricanes and earthquakes, but the concept is becoming more common in commercial and residential insurance. It’s called parametric because rather than responding to a specific loss, the coverage pays out when an agreed “metric” such as wind speed or ground shaking reaches or exceeds certain intensity. Insurers are offering such coverage based on a wide variety of other metrics, including barometric pressure, rainfall, average snowfall, river water levels, storm surge as measured by tide gauges and even hotel occupancy rates.