Time to Sell National Oilwell Varco?

Should you sell National Oilwell Varco (NYSE: NOV) today?

The decision to sell a stock you've researched and followed for months or years is never easy. If you fall in love with your stock holdings, you risk becoming vulnerable to confirmation bias -- listening only to information that supports your theories, and rejecting any contradictions.

In 2004, longtime Fool Bill Mann called confirmation bias one of the most dangerous components of investing. This warning has helped my own personal investing throughout the Great Recession and the recent volatility throughout early August. In this series, I want to help you identify potential sell signs on popular stocks within our 4-million-strong Fool.com community.

Today I'm laser-focused on National Oilwell Varco, ready to evaluate its price, valuation, margins, and liquidity. Let's get started!

Don't sell on price
Over the past 12 months, National Oilwell Varco has risen 69.1% versus an S&P 500 return of 9.1%. Investors in National Oilwell Varco have every reason to be proud of their returns, but is it time to take some off the top? Not necessarily. Short-term outperformance alone is not a sell sign. The market may be just beginning to realize the true, intrinsic value of National Oilwell Varco. For historical context, let's compare National Oilwell Varco's recent price to its 52-week and five-year highs. I've also included a few other businesses in the same or related industries:

Source: Capital IQ, a division of Standard & Poor's.

As you can see, National Oilwell Varco is down from its 52-week high. If you bought near the peak, now's the time to think back to why you bought it in the first place. If your reasons still hold true, you shouldn't sell based on this information alone.

Potential sell signs
First up, we'll get a rough idea of National Oilwell Varco's valuation. I'm comparing National Oilwell Varco's recent P/E ratio of 16.2 to where it's been over the past five years.

Source: Capital IQ, a division of Standard & Poor's.

National Oilwell Varco's P/E is lower than its five-year average, which could indicate the stock is undervalued. A low P/E isn't always a good sign, since the market may be lowering its valuation of the company because of less attractive growth prospects. It does indicate that, on a purely historical basis, National Oilwell Varco looks cheap.

Now, let's look at the gross margins trend, which represents the amount of profit a company makes for each $1 in sales, after deducting all costs directly related to that sale. A deteriorating gross margin over time can indicate that competition has forced the company to lower prices, that it can't control costs, or that its whole industry's facing tough times. Here is National Oilwell Varco's gross margin over the past five years:

Source: Capital IQ, a division of Standard & Poor's.

National Oilwell Varco has been able to grow its gross margin, which tends to dictate a company's overall profitability. This is great news; however, National Oilwell Varco investors need to keep an eye on this over the coming quarters. If margins begin to dip, you'll want to know why.

Next, let's explore what other investors think about National Oilwell Varco. We love the contrarian view here at Fool.com, but we don't mind cheating off our neighbors every once in a while. For this, we'll examine two metrics: Motley Fool CAPS ratings and short interest. The former tells us how Fool.com's 180,000-strong community of individual analysts rate the stock. The latter shows what proportion of investors are betting that the stock will fall. I'm including other peer companies once again for context.

Source: Capital IQ, a division of Standard & Poor's.

The Fool community is rather bullish on National Oilwell Varco. We typically like to see our stocks rated at four or five stars. Anything below that is a less-than-bullish indicator. I highly recommend you visit National Oilwell Varco's stock pitch page to see the verbatim reasons behind the ratings.

Here, short interest is at a mere 1.8%. This typically indicates few large institutional investors are betting against the stock.

Now, let's study National Oilwell Varco's debt situation, with a little help from the debt-to-equity ratio. This metric tells us how much debt the company's taken on, relative to its overall capital structure.

Source: Capital IQ, a division of Standard & Poor's.

National Oilwell Varco's total debt is around its five-year average. When we take into account increasing total equity over the same time period, this has caused debt-to-equity to decrease, as seen in the above chart. Based on the trend alone, that's a good sign. I consider a debt-to-equity ratio below 50% to be healthy, though it varies by industry.  National Oilwell Varco is currently below this level, at 3%.

The last metric I like to look at is the current ratio, which lets investors judge a company's short-term liquidity. If National Oilwell Varco had to convert its current assets to cash in one year, how many times over could the company cover its current liabilities? As of the last filing, National Oilwell Varco has a current ratio of 2.64. This is a healthy sign. I like to see companies with current ratios equal to or greater than 1.5.

Finally, it's highly beneficial to determine whether National Oilwell Varco belongs in your portfolio -- and to know how many similar businesses already occupy your stable of investments. If you haven't already, be sure to put your tickers into Fool.com's free portfolio tracker, My Watchlist. You can get started right away by clicking here to add National Oilwell Varco.

The final recap

National Oilwell Varco has failed none of the quick tests that would make it a sell. This is great, but does it mean you should hold your National Oilwell Varco shares? Not necessarily. Just keep your eye on these trends over the coming quarters.

In order to do that, I strongly recommend clicking here to add National Oilwell Varco to My Watchlist  to help you keep track of all of our ongoing coverage of the company.