Jack Shafer in Slate debunks the idea that broadsheets owe their rise solely to paper taxes.
Early printed and manuscript news sheets were often large to begin with, closer in size to today's magazines than to most novels. A full sheet of book paper (roughly 25 by 38 inches) folded in half two times produces a magazine format called a quarto, for the four leaves (eight pages) that result. Folded one more time, the sheet produces a book-sized format call an octavo. After the paper tax was imposed, some English octavo newspapers grew to the quarto size that had been common in early European news sheets.
If broadsheets owed their existence to a paper tax, then newspapers would have right-sized themselves to a different, optimum dimension after the British tax (a duty on paper) was discontinued in 1855, according to Barnhurst. Yet the broadsheet flourished for another century and a half in Britain before its "quality" dailies started printing in the tabloid format.
...what explains the endurance of the broadsheet myth? It isn't even plausible when you think it through: If you had been the British exchequer and a newspaper sidestepped taxes by inflating page-size, wouldn't you have closed the loophole the next day by declaring, "Publishers may print their newspapers on sheets of paper the size of a mainsail if they so desire, but it's this office's recommendation that the crown adopt a per square-inch tax on newspapers"? Yes, you would have, and the broadsheet would have expired overnight if it were not a viable format.
Scholar Kevin G. Barnhurst demolishes the broadsheet myth in his 1994 book Seeing the Newspaper, calling it "received history." No one factor explains the broadsheet's rise, he writes. Yes, the British did impose a new tax in 1712, but the "British tax on paper did not initiate relatively large newspaper formats," he writes.