How frequently will yellow, orange, and red PAGER alerts occur?

Over the past 38 years there would have been approx. 17,792 green, 568 yellow, 52 orange, and 49 red alerts. This frequency equates to approximately 15 yellow, 1-2 orange, and 1-2 red alerts per year. Domestically, in the United States, high-fatality alert levels are much less frequent due to improved building codes and practices in areas of high seismicity. Hence, domestic alerting based on economic impact may be more suitable for response purposes.