Most Powerful Force Impacting Stock Prices The change in a company's future earnings potential, as reflected in earnings estimate revisions, and the near-term price movement of its stock are proven to be strongly correlated. The influence of institutional investors has a partial contribution to this relationship, as these big professionals use earnings and earnings estimates to calculate the fair value of a company's shares. An increase or decrease in earnings estimates in their valuation models simply results in higher or lower fair value for a stock, and institutional investors typically buy or sell it. Their transaction of large amounts of shares then leads to price movement for the stock. For Siemens AG, rising earnings estimates and the consequent rating upgrade fundamentally mean an improvement in the company's underlying business. And investors' appreciation of this improving business trend should push the stock higher.