Just to nitpick, the standard deviation of a time series is not even well-defined unless we know that the series is stationary. In Shalizi’s words, “if you want someone to solve the problem of induction, the philosophy department is down the stairs and to the left”. If it were well-defined (e.g. if the time series were coming from some physical process with rigidly specified parameters), it would be just as observable as the mass of the moon, i.e. indirectly. That would fit my criteria for a “true number”.
I guess that for me a “true number” has to be a well-defined number that you can measure in multiple ways and get the same result, so inflation is out because it’s not well-defined, and CPI is out because it’s just one method of measurement that doesn’t agree with anything else.
Just to nitpick, the standard deviation of a time series is not even well-defined unless we know that the series is stationary. In Shalizi’s words, “if you want someone to solve the problem of induction, the philosophy department is down the stairs and to the left”. If it were well-defined (e.g. if the time series were coming from some physical process with rigidly specified parameters), it would be just as observable as the mass of the moon, i.e. indirectly. That would fit my criteria for a “true number”.
I guess that for me a “true number” has to be a well-defined number that you can measure in multiple ways and get the same result, so inflation is out because it’s not well-defined, and CPI is out because it’s just one method of measurement that doesn’t agree with anything else.