I've been woefully slack in disseminating the fascinating facts from Hubert Parkers 'The Hop Industry' (1934) so here's another chunk, this time on the amount of hops used in beer and where they came from:
"...it should be recalled that less hops are now used for brewing, i.e. there is a reduced rate of 'hopping'. For European countries, the present rate of hopping does not exceed 250 grams per hectolitre in most cases: for England it is rather more than double this amount, and in the Irish Free State it is about treble the continental rate of hopping. There rates are substantially lower than they were a generation ago and account for a proportion of the reduced demand for hops."
In modern terms 1000 grams per hectolitre is full blown craft beer dissolve your tongue standards so even in the dark days of depression they were still using a lot of hops in some pretty weak beers.
On the following page he has more details showing how many hops were needed for this:
"England is a very large consumer of hops, her annual consumption, home and imported, amounting to not much short of 30 percent of the world's total supply. Her imports of hops represent 5 per cent to 10 per cent of the production of the rest of the world. The record of the last thirty years shows that it is to America that England turn for the bulk of her foreign supplies. In very few years in this period did the importation of hops from America fall below 50 per cent of the total importation.: frequently it exceeded 75 per cent. On balance therefor the European hop growing countries, taken together, have contributed only about 40 per cent of our foreign supplies, while imports of hops of the Bavarian or Bohemian types are represented by a much smaller proportion."
The ending of prohibition in the USA caused problems for the British brewers:
"The increased demand for hops in America which has come about through the modification of the prohibition laws may result in English brewers having to take a larger proportion of English hops until American production of hops has adjusted itself to the new demand, and customs may veer round in the direction of an English 'hopped' beer. It need hardly be said that we could undoubtedly grow in this country hops in sufficient quantity to meet brewers' requirements, but so long as brewers insist on a mixtures, it is on America that the trade will mostly rely for the foreign portion of it's supplies."
American hops contained more alpha acid than English hops so provided more bitterness. Though the hops breeding programme at Wye College was by now well established and things were moving on from the old landrace varieties:
"But the trade is taking great interest in Professor Salmon's new varieties - some of which, it will be recalled, combine the virtues of the American and English hops - and is is hoped that he will be able to satisfy them with types of hops of this character, which will reduce, if not altogether obviate, the necessity for the use foreign hops."
Professor Salmon's hop breeding programme was highly successful, and all of the high-alpha varieties grown today contain hops bred by him in their ancestry. Germany and the USA are however by far the biggest growers of them.