Looking into the current session, Southern Inc. (NYSE:SO) is trading at $62.23, after a 1.39% drop. Over the past month, the stock decreased by 0.16%, but over the past year, it actually increased by 3.96%. With questionable short-term performance like this, and great long-term performance, long-term shareholders might want to start looking into the company's price-to-earnings ratio.

Assuming that all other factors are held constant, this could present itself as an opportunity for shareholders trying to capitalize on the higher share price. The stock is currently under from its 52 week high by 7.87%.

The P/E ratio is used by long-term shareholders to assess the company's market performance against aggregate market data, historical earnings, and the industry at large. A lower P/E can either represent a company's poor future earnings potential or a buying opportunity relative to other stocks. It shows that shareholders are less than willing to pay a high share price, because they do not expect the company to exhibit growth, in terms of future earnings.

Most often, an industry will prevail in a particular phase of a business cycle, than other industries.

Compared to the aggregate P/E ratio of the 23.78 in the Electric Utilities industry, Southern Inc. has a lower P/E ratio of 22.54. Shareholders might be inclined to think that the stock might perform worse than its industry peers. It's also possible that the stock is undervalued.

There are many limitations to P/E ratio. It is sometimes difficult to determine the nature of the earnings makeup of a company. Shareholders might not get what they're looking for, from trailing earnings.