Graphs you didn't get to see 3: Averages leaves per practica

Pictures have to be worth at least a thousand words to justify the added expense of including them in a book or article - and this one didn't quite make it. In my discussion of practicas in Printing and Prophecy, and the more detailed treatment in an upcoming AGB article, it turned out that I could summarize the changes in average pamphlet length pretty efficiently in words. But I still think the graph below neatly expresses how the two-gathering, eight-leaf format became predominant by the early fifteenth century and remained the standard through 1550. At that point, an additional gathering, or twelve leaves, became the norm for a few decades, followed by the addition of a fourth gathering in 1590 and later. The average number of leaves doesn't change smoothly, but rather with the granularity that comes from adding entire quarto signatures.

Average number of leaves in German practicas, 1480-1620

Generating this graph was one of the benefits of entering every edition that was relevant for Printing and Prophecy into a Microsoft Access database. Once the data was there, it was easy to select only the German practicas, drop the format field into an Excel spreadsheet, and turn the various format formulations into leaf counts through a combination of Excel formulas and manual editing. (An example from VD16 is "[10] Bl. : TH. ; 4"; it's not too difficult to tell Excel to grab only the parts between the square brackets.)

The following table summarizes how many practicas from each decade had known leaf counts (so excluding fragments), and the average as seen in the graph above.

	n	avg
1490	27	9.7
1500	39	9.2
1510	13	8
1520	42	7.9
1530	74	7.6
1540	75	8.7
1550	83	9.3
1560	50	13.4
1570	108	12.7
1580	159	12.8
1590	170	15.5
1600	183	16
1610	49	16.2
1620	38	17

And thus five years of intermittent data collection and an hour of fiddling with a database query and a spreadsheet yields three sentences of expository prose and one neat graph that didn't make it into print.