Coenraad Kleinhans wrote from South Africa to ask why one should ever use a Z Chart. Z charts are discussed on my web site in a PDF file at www.duncanwil.co.uk/pdfs/charting.pdf ... here's what I told Coenraad, though. The benefits of using a Z chart are that they contain three elements of a time series data set: the raw data, the cumulative data and the moving average data. Consequently, we are able to compare current data within the context of the present and the past. There is nothing wrong with plotting data sets on an XY or Line graph, of course, but to get the maximum benefit from the data, you would have to construct three of them to compete with the Z chart! In case you hadn't seen it, I have a pdf file at http://www.duncanwil.co.uk/pdfs/charts.pdf that illustrates the Z chart and a bit about how to construct one. You might find http://duncanwil.co.uk/pdfs/charting.pdf useful too. DW