A time-series series (cumulative sum) would also answer the question, and could actually be plotted on the same chart as the original series.

On a side note, time series is not a great phrase for the original data set ("time sequence" would have made more sense, since the numbers shown are not cumulative)

Yes, a cumulative sum would have done a much better job than that pie chart at illustrating their point (from the text: "Apple over the last four years spent more on R&D than it did during the preceding 15 years combined")

Also note that 'time series' is a well-defined and widely-used term that exactly describes the dataset presented here (http://en.wikipedia.org/wiki/Time_series).

But if that is displayed as a line chart, that clearly displays the year-over-year differences. So if someone wants to ask "what is the overall trend of spending over the past five years?" that is nearly impossible with the pie chart.

Pie charts are by far one of the worst forms of graphs ever devised and should be killed off as a concept for good, as in, please remove this from Excel.

Everyone is this thread is conveniently ignoring that the data is initially presented as a bar graph. The pie chart is secondary for a very narrow purpose, and it's far from terrible in this application.