There are 11 categories of securities included in the index: financial, energy, materials, industrial, consumer discretionary, telecommunications services, healthcare, consumer staples, utilities, information technology and real estate. The index has the most financial and energy constituents, followed by the materials and industrial categories. Its performance therefore heavily reflects how those industries are doing, and disturbances in the economy or oil price dips can have a big impact.Below we’ve broken down each of the 11 sectors as laid out by S&P Dow Jones Indices, and have listed the main players in each industry.