Comparing Standard of Living with National Income

Idea

Economists use national income statistics — chiefly GDP and GNI — to compare the material standard of living either over time (one economy across years) or over space (between economies). Raw figures mislead in both, and each limitation has a partial remedy. This is a neutral catalogue of those limitations, not a verdict on any one comparison.

Considerations

Comparing over time. A single economy’s figures must be adjusted for three moving parts:

Changes in the general price level. Nominal national income rises with inflation even when output does not, so real national income should be used to isolate the genuine change in output.
Changes in population. If population grows faster than real national income, the average person’s share falls even as the aggregate rises; real national income per capita corrects for this.
Changes in the composition of national income. Output is a mix of consumer and capital goods, but material standard of living derives only from consumption. An economy whose growth is concentrated in military or capital goods — or that is “belt-tightening” through heavy early-stage investment — raises measured output without a matching rise in current consumption.
Changes in the distribution of income. Real GDP per capita is an average that hides dispersion; growth captured by a small minority need not raise living standards for the majority. The Gini coefficient is used alongside it to track inequality.
Changes in data accuracy. Statistical capacity improves as an economy develops, so older figures are less reliable than recent ones, which can distort a long-run comparison.

Comparing over space. Comparisons between economies face the analogues, plus currency issues:

Different currencies. Each economy measures output in its own currency, so a common unit (often the US dollar) and an exchange rate are needed. Market exchange rates fluctuate and misrepresent purchasing power, since they ignore differences in the cost of living. The remedy is to convert at a purchasing power parity (PPP) exchange rate — the amount of each currency needed to buy a common basket of goods — which discounts cost-of-living differences. PPP markedly raises the measured living standards of developing economies, whose lower prices market rates understate. Its limitation is that the common basket must be specially constructed and cannot reflect every economy’s tastes.
Different population sizes, different compositions of national income, different distributions of income, and different sizes of the non-monetised sector (subsistence farming and unpaid household work, larger in developing economies) all distort cross-country comparison much as their over-time analogues do, and several have no clean statistical fix.
Different availability and reliability of data across economies means the same comparison mixes accurate and inaccurate figures.

Non-material standard of living is barely captured by national income at all. Growth often brings negative externalities — pollution, congestion — and disamenities — longer hours, higher stress — that lower the intangible quality of life even as output rises, so income figures can overstate the true change in well-being. This is why alternative indicators are needed for the non-material half.