The American School, also known as the "National System", represents three different yet related constructs in politics, policy and philosophy. It was the American policy from the 1860s to the 1970s, waxing and waning in actual degrees and details of implementation. Historian Michael Lind describes it as a coherent applied economic philosophy with logical and conceptual relationships with other economic ideas. During its American System period the United States grew into the largest economy in the world with the highest standard of living, surpassing the British Empire by the 1880s.