The sole determinant of the Zacks rating is a company's changing earnings picture. The Zacks Consensus Estimate -- the consensus of EPS estimates from the sell-side analysts covering the stock -- for the current and following years is tracked by the system. Therefore, the Zacks rating upgrade for Teradyne basically reflects positivity about its earnings outlook that could translate into buying pressure and an increase in its stock price. The change in a company's future earnings potential, as reflected in e ...