Wealth is presented as the sum of marketable goods and their prices, assessed for individuals and nations by what can be bought or sold. Natural advantages are excluded because they lack market prices and their valuation risks double-counting, while price movements can misleadingly alter measured wealth. The distinction between material goods and services is emphasized: only transferable services or the outputs they produce count as wealth, with personal skills normally reflected through the goods or paid services they help create. The production system is defined broadly to include all activities that generate tangible and intangible wealth, and critics are noted who urge consideration of social welfare beyond market values.