Looking into the current session, Mercury Systems Inc. MRCY shares are trading at $56.18, after a 0.1% gain. Moreover, over the past month, the stock increased by 2.64%, but in the past year, decreased by 20.25%. Shareholders might be interested in knowing whether the stock is undervalued, even if the company is performing up to par in the current session.

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The stock is currently above its 52 week low by 26.42%. Assuming that all other factors are held constant, this could present itself as an opportunity for investors trying to diversify their portfolio with Aerospace & Defense stocks, and capitalize on the lower share price observed over the year.

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.

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

Mercury Systems Inc. has a better P/E ratio of 80.2 than the aggregate P/E ratio of 31.63 of the Aerospace & Defense industry. Ideally, one might believe that Mercury Systems Inc. might perform better in the future than it's industry group, but it's probable that the stock is overvalued.

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.