Two major considerations differentiate marketing strategies from one another.

The first consideration is that the bottom line is what really matters. Having more people interested in your brand and talking about it is nice, but hearing someone mention your name on Twitter doesn't usually equate to making a sale.

For most marketers, the bottom line is what really counts. What's going to bring you in the most money?

The second consideration is that "good enough" isn't good enough; you want the best.

There are tons of marketing strategies out there, each with different possible returns and different demands. Many of them offer promising returns on your investment. But if you're going to pay X amount of money for a service, you don't want just a "positive" return—you want the greatest possible positive return.

With that in mind, you must find out which marketing strategy is the best one for you to use.

Objective metrics are hard to cite, however. Every business is going to see different results, and there's always the possibility that some of the businesses in our samples won't be using the strategies in question correctly. But there is one mathematical reason why SEO, when done properly, fulfills the above condition.

Compounding Interest

Most investors and savvy personal financiers will tell you the power of compound interest is astounding. It's why so many finance advice articles note that getting started early is one of the greatest keys to success, and it's responsible for spurring the financial growth of countless self-made millionaires.

The idea is that, as you start earning a consistent interest rate over a given period of time, your principle will grow. As your principle grows, your earned interest will grow, eventually snowballing into a bigger and bigger rate of return.

When implemented correctly, SEO is a strategy that utilizes the principle of compounding interest to yield bigger and bigger returns.

For example, when you create a blog post, you instantly gain some new search engine real estate and some inbound link potential. You may get a few hundred visitors in the first week—but that article never goes away. It will keep attracting links, keep earning new visitors, and continue earning your company more visibility and more revenue (especially with a strong call-to-action). As you add more related blog posts, you'll encounter the same pattern of growth.

Compare that to a more traditional marketing and advertising strategy. With pay-per-click ads, you spent a finite amount of money for a finite number of clicks. All in all, you might earn $2 in value for every $1 you spend, but that rate is going to remain consistent forever. You might see subtle increases because of text tweaks or the addition of a new marketing channel, but ultimately your growth has a ceiling.

A Multifaceted Strategy

You could argue that other strategies exhibit qualities similar to accrued compound interest. (Email marketing, for example, tends to grow in ROI as your subscription list gets bigger and bigger.) But there's still one advantage that SEO has over these potential contenders; it features exponential growth in multiple areas.

• Ranking. If your content is valuable, it will continue to earn links indefinitely, gradually increasing its individual page rank, and consistently moving it closer to the top spots for relevant queries. In parallel, new articles you create will evolve along similar lines, ultimately multiplying your growth in terms of total search rank.
• Readership. As you start publishing content more consistently and syndicating it on higher-profile channels, your readership will grow from almost nothing to larger and larger levels. If you're dedicated enough, eventually you'll get to a point of popularity that allows you to cumulate new readers simply because you have so many readers.
• Referral traffic. Every inbound link you build that points to your site passes domain authority, increasing your rank, but those external posts never really go away. That means those links are capable of sending new referral traffic your way for the indefinite future. So, the more links you build, the bigger the effect will be.
• Visibility. Overall visibility will come to you through many channels, including the new publishers you build relationships with, the influencers you engage with, and the social media followers you attract. Each new point of visibility gives you new directions for growth, giving you a never-ending path to improvement.

Moreover, depending on what strategies you use as part of your SEO campaign, there might even be more benefits.

As long as you remain consistent in your efforts and adapt your strategy to reflect changes (such as Google updates and user interests), a well-rounded SEO strategy can earn a far higher ROI than any other strategy in the long term.

The only caveat to this claim is the fact that SEO actually comprises other strategies that could be used independently, such as content marketing and social media marketing. So, it may take a while to get going, but once you establish a foundation, you'll start to see compounding returns on your investment.