Area charts are valid only if the area is meaningful. There certainly are cases where it can make sense to use a visualization based on filled, stacked areas. L

Area charts are valid only if the area is meaningful. There certainly are cases where it can make sense to use a visualization based on filled, stacked areas. Look at, for example, Weatherspark.com's colortemp visualization for historical weather trends, which shows 'percentage of time when temperature is in a particular band' over a time axis. That's a good visualization, because the quantity makes physical sense - integrating 'time in band per day' over 'days' gives you overall 'time in band'. Integrating 'market share' over 'months' gives you 'market share months', which is a meaningless value.