Value of stock

Financial ratio averages and analysis benefits me in understanding stock performance and valuation of a company. The Dow Jones and S&P 500 are essential tools which assist me in understanding the current performance of company stocks as it pertains to the market. If I notice a specific industry is not performing well, I may need to sell stocks within that specific industry and purchase stocks in another industry which is showing consistent and positive performance. These two tools (as well as other calculations and tools) help me to make additional calculations in regards to my financial portfolio. 

Why does the value of a share of stock depend on dividends?