For the timing in the WM8S_Morse library, I used the ARRL's Morse code speed calculations published in April 1990's QST (A Standard for Morse Timing Using the Farnsworth Technique by Jon Bloom, KE3Z) to convert character speed in WPM (c in the ARRL's calculations) and overall speed in WPM (s in the ARRL's calculations) to determine the total Farnsworth delay (t(a)) that must be spread out over the inter-character space (t(c)) and inter-word space (t(w)), the dit mark / space time (i.e., one element time, or u in the ARRL calculations), and the dah mark time, all maintaining the standard 1:1:3:7 ratio:

http://www.arrl.org/files/file/Technology/x9004008.pdf

The ARRL uses the more-or-less standard word PARIS, with 31 units of element mark and element space time plus 19 units of inter-character and inter-word space, or 50 total elements, for its calculations.

In order to see if PARIS and its 50 total elements still represented a decent "word" for words-per-minute calculations of a common amateur radio QSO, I took:

• 1,000 of the most common English words
• the words making up the names of the 100 largest cities in the world
• the numbers 1 through 30
• eight of what I considered common power levels (5W, 10W, 25W, 50W, 100W, 200W, 500W, and 1KW),
• the most common Morse prosigns,
• the 200 highest scoring callsigns from the 2014 IARU HF contest results,
• what I think are the 25 most common Q-signals,
• and 150 common Morse abbreviations (like PSE, UR, ES, etc.),

and I came up with the following statistics:

First, the mean number of elements per word is 49.489. So as it turns out, in that regard, at least, PARIS is still a pretty good word for our purposes.

I'd also eventually like to support weight and ratio, however, and that will require determining the average number of dits, dahs, inter-element space, inter-character space, and inter-word space per word. And in that regard, PARIS doesn't stack up as well.

If you care of about these sorts of things, µ number of dits per word = 7.307; µ number of dahs per word = 5.431; µ number of inter-element spaces per word = 8.162; µ number of inter-character spaces per word = 3.575; and number of inter-word spaces = 1.000 (by definition).