As such, the Zacks rating upgrade for Lonza Group Ag is essentially a positive comment on its earnings outlook that could have a favorable impact on its stock price. 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.