In the current session, STMicroelectronics Inc. STM is trading at $46.13, after a 1.62% increase. Over the past month, the stock increased by 8.96%, and in the past year, by 47.96%. With performance like this, long-term shareholders are optimistic but others are more likely to look into the price-to-earnings ratio to see if the stock might be overvalued.

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 higher from its 52 week high by 1.31%.

The P/E ratio measures the current share price to the company's earnings per share. It is used by long-term investors to analyze the company's current performance against its past earnings, historical data and aggregate market data for the industry or the indices, such as S&P 500. A higher P/E indicates that investors expect the company to perform better in the future, and the stock is probably overvalued, but not necessarily. It also shows that investors are willing to pay a higher share price currently, because they expect the company to perform better in the upcoming quarters. This leads investors to also remain optimistic about rising dividends in the future.

Depending on the particular phase of a business cycle, some industries will perform better than others.

Compared to the aggregate P/E ratio of the 58.19 in the Semiconductors & Semiconductor Equipment industry, STMicroelectronics Inc. has a lower P/E ratio of 27.85. 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.