Low Gravities

In the second half of the 19th century a new type of beer appeared in the UK: Light Bitter.

The early Pale Ales were all brewed in the Burton mould as Stock Ales. That is beers that underwent extensive ageing before sale. And when I say extensive, I mean extensive. Bass Pale Ale for example, was over a year old before sale, even domestically. The version sent to India was 12 months old before it even left the brewery.

"Low Gravities.
THE tendency for light beers seems to be on the increase, and we cannot quite understand why brewers should not make large profits, more especially when the public demand a beverage constituting nothing more nor less than a dry, thoroughly fermented beer, containing but small percentages of sugar and albumenous matters, with a somewhat high percentage of alcohol. There is surely no difficulty in producing such a beverage, and if mashing operations are conducted in a manner favouring the minimisation of these objectionable bodies, and the extract constitutes that of a dry sugar such as cone or glucose, we venture to say that a beverage of this character would answer family customers much better than the ordinary publichouse mild ales of somewhat high gravities and containing as they do, comparatively speaking, high percentages of azotised and sugar bodies. More attention should be paid to this question than readers are aware, for in these days of increasing competition, when it is indeed hard to buy publichouses at reasonable prices, there remains but one alternative, and that is (to those brewers who cannot afford to pay fancy prices for houses) if they are to hold their own, much less increase their trade, they must undoubtedly cultivate a family trade; and we are bound to assert that hundreds of brewers, instead of giving proper attention to this class of customers, are too prone to forward the ordinary publichouse mild ale, which we need hardly say is anything but pleasant for the family trade."
"The Brewers' Guardian 1889", 1889, pages 317-318.

By "family use" they mean beer consumed at home. Which at this time was still mostly in the form of draught beer. The advertisements brewers placed in newspapers for this home trade are a great source of information about exactly what beers were being brewed by a specific brewery. Light Bitter, especially AK, is often praised in such adverts as being perfect for family use.

Here's an example of what the author was talking about, from Fullers of London:

Fullers Mild and Bitter in 1887
Beer	Style	OG	FG	ABV	App. Atten-uation	lbs hops/ qtr	hops lb/brl
AK	Pale Ale	1049.6	1014.1	4.69	71.51%	7.61	1.66
XX	Mild	1064.8	1023.3	5.50	64.10%	6.64	1.93
X	Mild	1054.6	1020.5	4.51	62.44%	6.64	1.63
IPA	IPA	1060.9	1016.6	5.86	72.73%	12.38	3.45
XKK	Pale Ale	1055.1	1015.2	5.28	72.36%	12.36	3.12
XK	Pale Ale	1057.1	1016.1	5.42	71.84%	11.58	2.84
Source:
Fullers brewing record held at the brewery

AK had the lowest OG of all their Bitters and Milds, though, due to the higher degree of attenuation, the ABV is higher than X Ale's. You can also se that AK was sinificantly more lightly hopped than Fuller's other Pale Ales. In fact the hopping rate wasn't much higher than for the Milds