They may find it difficult to make decisions based on rating upgrades by Wall Street analysts, as these are mostly driven by subjective factors that are hard to see and measure in real time. Therefore, the Zacks rating upgrade for First Community Bancshares basically reflects positivity about its earnings outlook that could translate into buying pressure and an increase in 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.