Is Illumina's Stock Expensive or Cheap by the Numbers?

Numbers can lie -- but they're the best first step in determining whether a stock is a buy. In this series, we use some carefully chosen metrics to size up a stock's true value based on the following clues:

• The current price multiples.
• The consistency of past earnings and cash flow.
• How much growth we can expect.

Let's see what those numbers can tell us about how expensive or cheap Illumina (Nasdaq: ILMN) might be.

The current price multiples
First, we'll look at most investors' favorite metric: the P/E ratio. It divides the company's share price by its earnings per share -- the lower, the better.

Then, we'll take things up a notch with a more advanced metric: enterprise value to unlevered free cash flow. This divides the company's enterprise value (basically, its market cap plus its debt, minus its cash) by its unlevered free cash flow (its free cash flow, adding back the interest payments on its debt). Like the P/E, the lower this number is, the better.

Analysts argue about which is more important -- earnings or cash flow. Who cares? A good buy ideally has low multiples on both.

Illumina has a P/E ratio of 31.9 and an EV/FCF ratio of 11.4 over the trailing 12 months. If we stretch and compare current valuations to the five-year averages for earnings and free cash flow, Illumina has a P/E ratio of 359.3 and a five-year EV/FCF ratio of 24.4.

A positive one-year ratio under 10 for both metrics is ideal (at least in my opinion). For a five-year metric, under 20 is ideal.

Illumina is zero for four on hitting the ideal targets, but let's see how it compares against some competitors and industry mates. 

Source: S&P Capital IQ; NM = not meaningful because of losses.

Numerically, we've seen how Illumina's valuation rates on both an absolute and relative basis. Next, let's examine...

The consistency of past earnings and cash flow
An ideal company will be consistently strong in its earnings and cash flow generation.

In the past five years, Illumina's net income margin has ranged from -81.7% to 13.4%. In that same time frame, unlevered free cash flow margin has ranged from 0% to 27.2%.

How do those figures compare with those of the company's peers? See for yourself:

Source: S&P Capital IQ; margin ranges are combined.

Additionally, over the last five years, Illumina has tallied up four years of positive earnings and five years of positive free cash flow.

Next, let's figure out...

How much growth we can expect
Analysts tend to comically overstate their five-year growth estimates. If you accept them at face value, you will overpay for stocks. But while you should definitely take the analysts' prognostications with a grain of salt, they can still provide a useful starting point when compared to similar numbers from a company's closest rivals.

Let's start by seeing what this company's done over the past five years. In that time period, Illumina has put up past EPS growth rates of 25.4%. Meanwhile, Wall Street's analysts expect future growth rates of 18%.

Here's how Illumina compares to its peers for trailing five-year growth (because of losses, the trailing growth rates for Affymetrix and Luminex aren't meaningful):

Source: S&P Capital IQ; EPS growth shown.

And here's how it measures up with regard to the growth analysts expect over the next five years:

Source: S&P Capital IQ; estimates for EPS growth.

The bottom line
The pile of numbers we've plowed through has shown us the price multiples shares of Illumina are trading at, the volatility of its operational performance, and what kind of growth profile it has -- both on an absolute and a relative basis.

The more consistent a company's performance has been and the more growth we can expect, the more we should be willing to pay. We've gone well beyond looking at a 31.9 P/E ratio, and we see that its EV/FCF ratios are much more attractive. This is due to (1) free cash flows exceeding earnings, and (2) a net cash balance (i.e., more cash than debt). One thing to remember, though, is that free cash flow takes out Illumina's cash acquisitions (that hits later in the cash flow statement).

Looking at Illumina's margins, there really was only one negative number ... the scary -81.7% figure. The back story is that earnings were hit by acquired in-process research and development in 2007. Otherwise, Illumina's margins are positive and its growth over the last five years has been strong.

Note that Illumina has been a Motley Fool Stock Advisor recommendation since 2008, but so far we've only looked at the initial numbers. If you find Illumina's numbers or story compelling, don't stop. Continue your due diligence process until you're confident one way or the other. As a start, add it to My Watchlist to find all of our Foolish analysis.

To see the stocks that I've researched beyond the initial numbers and bought in my public real-money portfolio, click here.