There are lots of ways you can invest in online marketing, from banner ads and email marketing to social media. But, when it comes to lead generation it’s becoming more and more apparent that the best use of your time and money is search engine optimization (SEO). Because SEO can tell you a lot about what potential clients are responding to, it shouldn’t be just another part of your online marketing arsenal. It should be the foundation of your strategy.

In an effort to weigh the efficacy of online marketing tools, Hinge surveyed 500 professional services firms. The firms were broken out into high growth and average growth. Thrown in the mix for good measure was a group of 20 online marketing experts. Guess what the high growth and expert firms picked as the top technique for yielding online marketing results?

As you can see, SEO is the clear winner among the growers and knowers. But, if you’re like most, the proof is in your own numbers, not anyone else’s. That’s why it’s important to know how to measure SEO. There are three metrics that are key to understanding the impact of your SEO efforts. Let’s take a look:

1. Traffic

Everyone thinks to measure search rankings (“Are we on page 1 yet?”), but traffic is the metric that matters. Whether your ranking first or fifty-first place in Google searches won’t matter if no one is searching keywords that lead them to your website. But if you monitor organic search traffic and the keyword searches that bring visitors to your site, you’ll see that just how many views Google is sending you.

2. Conversion

Once you’ve got the eyeballs aimed intently on your site, you’re done, right? Success achieved!

Well, no. Don’t lose sight of the fact that conversion is one of the top goals of your online marketing efforts. And the goal of SEO is to drive relevant traffic to your site. Keyword relevant—meaning these visitors are looking for something you can offer. All the traffic in the world is irrelevant if it doesn’t result in conversion. How to measure SEO effectiveness? Measure conversions.

Are your visitors downloading a piece of content, filling out a contact form, registering for a webinar? Conversions can be any of the above and more—depending on the outcome you’re looking for. What do you want them to do once they’re on your site?

Google analytics makes it simple to set up goals and monitor conversions. You’ll be able to see what keywords and keyword phrases are creating conversions—and which aren’t. By tracking these metrics, you’ll see what’s working and what’s not.

Remember, the key to knowing your SEO is getting the right results is knowing how much of your traffic is taking action. When the goal of your SEO and other online marketing efforts is lead generation and business growth, passive traffic is barely better than none at all.

3. Behavior

In addition to conversions—forms filled out, content downloaded, etc.—you can use your analytics to measure visitor behavior. Google gives weight to things like the amount of time visitors spend on your site, how many pages they view, comments, shares via social media, and so on. By seeing the pages visitors view (and convert on), as well as these other metrics, you can form a thorough picture of what’s working in your SEO efforts—and on your website. Once you determine what’s working, you can concentrate your efforts on those techniques or concepts, while letting go of—or retooling—those that aren’t.

Remember Figure 1? Not only do expert users of SEO find it effective but high growth firms do as well. The correlation is clear: effective use of SEO will lead to high growth. Once you know how to measure SEO efficacy, you’re on track to understanding the behavior of your potential clients. Stay on that track and you’re sure to find growth.