Its like watching the tachometer to tell what speed you are going, without knowing what gear you are in. Its just a measure of total spending on newly produced stuff. Its not a measure of economic productivity, its not a measure of net new real wealth, ...

... someone using GDP to assess standard of living is like a nurse trying to measure my Blood Pressure with a thermometer. Its inability to do that is no failing of the thermometer ~ but of the nurse using the wrong tool for the job.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.