I thought it was a common term, but maybe that was back in the USENET days and the concept has been forgotten.
Here's a definition. Basically, real horsepower is the product of RPM and torque at some point on the load curve (typically the point at which the product is highest); "Sears horsepower" is the product of no-load RPM (zero torque, ergo no power) and stall torque (zero RPM, ergo no power). This tends to be a much larger number than would be obtained at any actual point along the load curve, especially for cheap motors.
Now realize that "market capitalization" is calculated in much the same way, as is the total "value" of securities markets: the product of two non-concurrent measurements.
Gets even more interesting if you factor in inconstant units. At least a horsepower is consistently somewhere around 750 Watts (depending on whether you're looking at metric or UK units), and the value of the Watt is well-defined and constant. Imagine if we had Watt inflation, and the 2015 Watt-hour did only half as much work as a 2008 Watt-hour...?