The colors of visible light, often referred to as ROY G BIV (for red, orange, yellow, green, blue, indigo, and violet), are a small portion of the entire electromagnetic spectrum. Light can be thought of as a stream of packets of energy called photons.
The United States has a mixed economy and has maintained a stable overall GDP growth rate, a moderate unemployment rate, and high levels of research and capital investment. Its seven largest trading partners are Canada, China, Mexico, Japan, Germany, South Korea, and the United Kingdom.
As of 2017, the United States has the world's largest economy and China the second largest. The International Monetary Fund estimates that China's economy has overtaken that of United States in terms of GDP (PPP) in 2014.