Economic growth within a country is influenced by four key factors: investment in human capital through education and training; investment in capital goods like machinery and technology; availability of natural resources; and level of entrepreneurship. A country's gross domestic product, which measures the total value of goods and services produced domestically in a year, is used to measure economic growth and standard of living. For a country to have sustained economic growth and a rising standard of living, it needs ongoing investments in both human and physical capital.