And this may be a stretch, but I do wonder if the popularity (and necessity) of coffeshop discussion was due in part to the crippling British copyright system depriving people of access to books, which started in the beginning of the 18th century:
http://www.spiegel.de/international/zeitgeist/no-copyright-l...
EDIT: And before the copyright system, the crippling monopoly over publishing enjoyed by the Stationers Company, which took hold in the early 15th century. My point being that Britain had long endured a stifling of written discourse, possibly encouraging verbal discourse in its stead.
http://www.ncbi.nlm.nih.gov/pubmed/18043953
I rather suspect that correlating caffeine to GDP would be even more difficult. Either way, the article doesn't even try to support these assertions factually. Which is OK -- it's a well-written article on an interesting subject. It's just good to keep in mind that some of the material is highly speculative.
Tuchman mentions our modern bewilderment at the insanely rash and reactionary decisions that were often taken by nobility in those times - declarations of war, terrible combat strategy and so forth, and which affected so many lives (mostly those of the poor). She goes on to speculate that these decisions make sense in the context of near-permanent drunkenness.
This an entirely different scenario from entirely replacing water with alcohol and being at least slightly drunk all the time. Not "all the time" as in "every weekend" but every hour of the day, including work.
Like I said, it's a complex area of research. If you think you're able to draw any meaningful conclusions based on your own intuition, then I think you're being a tad simplistic.
>>Remember — until the mid-seventeenth century, most people in England were either slightly — or very — drunk all of the time. Drink London’s fetid river water at your own peril; most people wisely favoured watered-down ale or beer (“small beer”). The arrival of coffee, then, triggered a dawn of sobriety that laid the foundations for truly spectacular economic growth in the decades that followed as people thought clearly for the first time. The stock exchange, insurance industry, and auctioneering: all burst into life in 17th-century coffeehouses — in Jonathan’s, Lloyd’s, and Garraway’s — spawning the credit, security, and markets that facilitated the dramatic expansion of Britain’s network of global trade in Asia, Africa and America.