Casual empiricism: the size of tea cups

Assume that persons in every country need the same volume of stimulants like tea or coffee to make it through the day, whether in Fargo or Faridabad. The smaller your tea-cup, the more breaks you require in order to get your daily quota. So, I dont think it is a coincidence that human productivity varies directly with the average size of beverage containers. The point can be made starkly by comparing the productivity of workers in Chicago, with its Grande Lattes and Calcutta, with its microscopic earthen bhaars. And of course there is endogeneity, with industrious races choosing larger cups and the not-so-industrious types self-selecting smaller ones. While you mull over this theory, I will go fix myself a tea.
Now, where did I put my imported bhaar.