National Australia Bank Ltd. (NABZY) could be a solid addition to your portfolio given its recent upgrade to a Zacks Rank #2 (Buy). An upward trend in earnings estimates -- one of the most powerful forces impacting stock prices -- has triggered this rating change.

The Zacks rating relies solely on a company's changing earnings picture. It tracks EPS estimates for the current and following years from the sell-side analysts covering the stock through a consensus measure -- the Zacks Consensus Estimate.

Individual investors often find it hard to make decisions based on rating upgrades by Wall Street analysts, since these are mostly driven by subjective factors that are hard to see and measure in real time. In these situations, the Zacks rating system comes in handy because of the power of a changing earnings picture in determining near-term stock price movements.

Therefore, the Zacks rating upgrade for National Australia Bank Ltd. 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, has proven to be strongly correlated with the near-term price movement of its stock. That's partly because of the influence of institutional investors that use earnings and earnings estimates for calculating 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 National Australia Bank Ltd. 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.

Harnessing the Power of Earnings Estimate Revisions

Empirical research shows a strong correlation between trends in earnings estimate revisions and near-term stock movements, so it could be truly rewarding if such revisions are tracked for making an investment decision. Here is where the tried-and-tested Zacks Rank stock-rating system plays an important role, as it effectively harnesses the power of earnings estimate revisions.

The Zacks Rank stock-rating system, which uses four factors related to earnings estimates to classify stocks into five groups, ranging from Zacks Rank #1 (Strong Buy) to Zacks Rank #5 (Strong Sell), has an impressive externally-audited track record, with Zacks Rank #1 stocks generating an average annual return of +25% since 1988. You can see the complete list of today's Zacks #1 Rank (Strong Buy) stocks here >>>>.