Are ozone exceedance rates decreasing ? Comment on " Extreme value analysis of environmental time-series : An application to trend ( eIection ill ground-level ozone " by

R.L. Smith (1989) in his Statistical Science discussion paper, proposed new methods for analyzing extreme values based on the point process view of highlevel exceedances, and illustrated them with a detailed analysis of ozone data from Houston, Texas. The methods are powerful and, in particular, the point process of cluster peaks over a high threshold provides a remarkable condensation of the massive data set that he analyzes. It inv,,lves little loss of relevant information and permits fairly simple analyses.