As an investor its worth striving to ensure your overall portfolio beats the market average. But the risk of stock picking is that you will likely buy under-performing companies. Unfortunately, that's been the case for longer term National Grid plc (LON:NG.) shareholders, since the share price is down 13% in the last three years, falling well short of the market return of around 18%.

With that in mind, it's worth seeing if the company's underlying fundamentals have been the driver of long term performance, or if there are some discrepancies.

In his essay The Superinvestors of Graham-and-Doddsville Warren Buffett described how share prices do not always rationally reflect the value of a business. By comparing earnings per share (EPS) and share price changes over time, we can get a feel for how investor attitudes to a company have morphed over time.

During the unfortunate three years of share price decline, National Grid actually saw its earnings per share (EPS) improve by 1.8% per year. Given the share price reaction, one might suspect that EPS is not a good guide to the business performance during the period (perhaps due to a one-off loss or gain). Alternatively, growth expectations may have been unreasonable in the past.

Given that EPS is up and the share price is down, it seems clear the market is less excited about the business than it was. Having said that, if the EPS gains continue we'd expect the share price to improve, longer term.

The company's earnings per share (over time) is depicted in the image below (click to see the exact numbers).

This free interactive report on National Grid's earnings, revenue and cash flow is a great place to start, if you want to investigate the stock further.

What About Dividends?

As well as measuring the share price return, investors should also consider the total shareholder return (TSR). The TSR is a return calculation that accounts for the value of cash dividends (assuming that any dividend received was reinvested) and the calculated value of any discounted capital raisings and spin-offs. Arguably, the TSR gives a more comprehensive picture of the return generated by a stock. We note that for National Grid the TSR over the last 3 years was 11%, which is better than the share price return mentioned above. This is largely a result of its dividend payments!

A Different Perspective

National Grid shareholders gained a total return of 6.4% during the year. But that return falls short of the market. It's probably a good sign that the company has an even better long term track record, having provided shareholders with an annual TSR of 8% over five years. It's quite possible the business continues to execute with prowess, even as the share price gains are slowing. While it is well worth considering the different impacts that market conditions can have on the share price, there are other factors that are even more important. Take risks, for example - National Grid has 4 warning signs (and 3 which shouldn't be ignored) we think you should know about.

Of course National Grid may not be the best stock to buy. So you may wish to see this free collection of growth stocks.

Please note, the market returns quoted in this article reflect the market weighted average returns of stocks that currently trade on British exchanges.

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This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.