Summary: Measure productivity as the time you spend working minus the time you spend working on stuff that's not useful. This definition of productivity doesn

Summary: Measure productivity as the time you spend working minus the time you spend working on stuff that's not useful. This definition of productivity doesn't even have the right units (time belongs in the denominator, not the numerator), and the analysis in the blog is muddled (why exactly does it matter whether or not I count lunch as 'non-value-added' since I'm going to subtract it anyway?)