I'm going to go with Planck's Constant for their collective intelligence.
(For those who don't know, planks constant is 6.62606957 × 10 to the -34th power)
But I may have underestimated the depths of their stupidity.
I wouldn't be able to say with assurance that it's even a positive number, no matter how infinitesimal. When talking about more than one stupid moonbat, we must remember the effect of their combined stupidity is not merely additive, but a complex inverse logarithmic progression which may well cross the
x axis at some point, rather than merely approaching it asymptotically.