There has always been a school of thought that asserts that the moon affects our sanity. In the eventful denouement to Othello, for example, as the tragedy of errors is unveiled, the distracted Moor detects its baleful influence: It is the very error of the moon; She comes more near the Earth than she was wont And makes men mad.
Othello's theory, of course, has no scientific basis what so-ever. But some time ago, an American scientist called Robert Currie suggested a rather roundabout way by which the moon might, just about, affect the collective sense of well-being of the human race.
Currie recalled that an American economist, Simon Kuznets, had identified in the early 1930s an alleged economic pattern called "Kuznets's long swings". It was alleged that the US economy varied in a more or less regular cycle of about 20 years, during which agricultural and industrial production, financial investment and various demographic indicators could be seen to rise, and then decline again. I suppose it follows that somewhere Mr Kuznets must have detected "short", or even "tiny", swings as well, but those are irrelevant for the present argument.
In any event, these long swings struck a familiar chord with Mr Currie. He remembered that the moon exerts a tidal influence on our atmosphere, which produces a very small twice-daily rise and fall in barometric pressure. Moreover, because of peculiarities in the moon's orbit, this tidal effect varies in magnitude over the decades, one component of the variation having a cycle of about 18.6 years.
Currie's next step was to connect this 18-year cycle to the weather, and this he claimed to have done by relating it to US rainfall figures. He conveniently discovered a corresponding cycle in the rainfall, with wet years in 1917, 1936, 1954, and 1973 - all coinciding with times of maximum lunar tidal force. It was then easy enough to relate this information to grain yields in the US, which very credibly show excellent yields in years of plentiful rain. The penultimate step was to postulate that variations in crop production would ripple through the largely agrarian US economy - and produce the "long swings" recognised by Kuznets.
The last link with lunacy was sociological. It is reasonable to believe that downturns in economic activity lead to political unrest and social discontent, while conversely, a long upward swing is conducive to lessening tensions, buoyant hopes, and a mood of optimism in the general populace. So by this complex luni-economic theory, civil disturbance and public euphoria - in the US at any rate - could be directly traced to the orbital idiosyncrasies of Earth's nearest neighbour.