Each stock market index slightly differs from others, and the index details such as components, weighting, calculation and trading hours must be studied. Fundamentally, factors that can affect equity prices, like earnings reports, or represented sectors, like new regulations, have a strong impact on the index. Economic data, like GDP, can also affect the price by stirring the valuation currency. Technically, the relative stability of the trends makes support and resistance levels reliable indicators for price targets and reversal points.