Economists have long studied labour’s share of national income as a crude indicator of income distribution. More recently, labour’s share has also been seen as offering insights into the shape of the aggregate production function. This has made labour’s share a parameter of interest for macroeconomics, growth economics, and international economics, among other fields. Recent studies support the long-standing observation that labour’s share of national income is relatively constant over time and across countries. Measurement of labour income, however, can be difficult in economies where many people are self-employed or work in family enterprises.