Investors might want to bet on American Tower (AMT) , as it has been recently upgraded to a Zacks Rank #2 (Buy). This upgrade primarily reflects an upward trend in earnings estimates, which is one of the most powerful forces impacting stock prices. 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. Indiv ...