When did Scottish Pale Ale stop being biiter?

I have wondered for a while when Scottish Pale Ales took on their current malty form. Then I realised that I had the information. I just needed to put it together.

For my new Scottish book I've assembled over 250 recipes so far. Including a load from William Younger. Which means I've calculated IBUs for their Pale Ales covering about a century. Isn't that cool?

I assembled the table for the new book. Which is coming along very nicely, thank you. I aim to have a complete first draft completed in two or three weeks. That's if I can keep my current pace. I've managed to bang out 7,000 words so far this week. Another 12,000 or so and I should be done.

Getting back to the topic, the table below makes it very obvious when all the bitterness was sucked out of Scottish beer. And what a surprise - it turns out to be WW I. With a further, smaller drop in the 1930's. Though there was also a considerable reduction between the 1850's and the 1860's.

There's one more question answered. Just another 9,488,277 to go.

William Younger Pale Ale bitterness 1851 - 1949
Year	Beer	OG	IBU
1851	XP	1058	180
1851	XXP	1072	217
1858	Ex Pale Ale	1063	142
1868	XP	1051	73
1868	XXP	1052	73
1879	XP	1052	99
1879	2XP	1046	76
1885	XP	1054	100
1885	XP Scotch	1055	87
1898	XP Scotch	1053	80
1913	LAE	1045	78
1914	SLE	1055	83
1921	XXPS	1046	36
1933	XXP	1043	34
1933	Expt	1054	53
1933	XXPS	1049	33
1039	XXPS	1046	13
1940	XP Btlg	1033	18
1949	XXP Btlg	1031	14
1949	XXPS	1037	21
1949	XXP	1031.5	19
Sources:
William Younger brewing records held at the Scottish Brewing Archive, document numbers WY/6/1/2/3, WY/6/1/2/28, WY/6/1/2/31, WY/6/1/2/45, WY/6/1/2/58, WY/6/1/2/63, WY/6/1/2/70, WY/6/1/2/76 and WY/6/1/2/88.