Recently, investor sentiment has become the focus of many studies on asset pricing. Research has demonstrated that changes in investor sentiment may trigger changes in asset prices, and that investor sentiment may be an important component of the market pricing process. Some authors suggest that shifts in investor sentiment may in some instances better explain short-term movement in asset prices than any other set of fundamental factors. In this paper we develop an Equity Market Sentiment Index from publicly available data, and we then demonstrate how this measure can be used in a stock market setting by studying the price movements of a group of firms which represent a stock market index. News events that affect the underlying market studied are quickly captured by changes in this measure of investor sentiment, and the sentiment measure is capable of explaining a significant proportion of the changes in the stock market index.