According to Matt:
The chart is based on "The Line of Elros: Kings of Númenor" from Unfinished Tales. It took around 3 hours to create the chart. I input the data into Excel and used that program to produce the chart.
The impetus was that I participate in online discussions with others on Tolkien's writing. The nucleus of the group are "Silmarillionaires" who can be heard on the Tolkien Professor's "Silmarillion Seminar."
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