But they aren't directly measurable and it is reasonable to expect that they might be estimated with considerable error. Finally, though, there are important economic concepts for which measurement can only be regarded as impossible. Sometimes this is because they are complete abstractions, where measurement depends entirely on an assertion that some observable thing is ‘really’ the abstract thing.
Rasheed Mohammed Al Maraj: Improving risk management in Bahrain Address by His Excellency Rasheed Mohammed Al Maraj, Governor of the Central Bank of Bahrain, at the 2nd Annual GCC Regulators’ Summit, Manama, 19 February 2008.