5. Six Sigma

Fourteen percent of organizations surveyed by HDI use Six Sigma today, with an additional 9 percent planning to use the business process going forward.

Six Sigma is focused on manufacturing and producing better quality products, and is intended for mid- to upper-level project managers, process engineers, consultants and manufacturing engineers. It was introduced by Bill Smith of Motorola in 1986, and popularized by former General Electric CEO Jack Welsh in the 1990s. 

Three certifications are offered in Six Sigma, which are intended to teach employees how to analyze, solve problems and improve existing processes in a production manufacturing setting. The most popular of these is the Six Sigma Green Belt, which is held by 66 participants in Global Knowledge's 11,000-person survey and offers an average salary of $101,038.