Whether you're a full-time marketer or a business manager who wears several hats throughout the day, odds are you want to know how well your marketing efforts are performing. After all, if you don't know what's working (and what's not), then you'll never be able to make improvements to your strategy. It's like they say: "You can't improve what you can't measure."

Of course, there are a ton of marketing metrics out there that companies swear by. These include cost per thousand impressions (CPM), cost per conversion (CPC), and perhaps the most popular one, return on ad spend (ROAS). In fact, many marketers view ROAS as the lodestar for their analytics, and use it as their "bottom line metric."

We could really "get into the weeds" with what ROAS is and how it works. For the sake of simplicity, here are the broad strokes on this metric:

• You can calculate ROAS using a simple formula: just divide the revenue directly tied to your campaign by advertising costs. It looks something like this: ROAS = revenue/advertising costs.
• ROAS only focuses on the immediate revenue that's generated by an ad or marketing campaign.
• Many executives love ROAS because it demonstrates tangible results from specific marketing initiatives.

ROAS has several limitations, but perhaps the single biggest one is this:

ROAS does not take into account all of the revenue that a marketing campaign may generate for the company.

For example, imagine that a customer sees a digital advertisement at the beginning of March. The ad sticks in the customer's mind for a couple of months. Then, in the middle of May, he or she finally decides to purchase the featured product from your company. In many cases, you wouldn't factor that purchase into your ROAS calculation. It came to fruition two and a half months later. However, it was still a direct result of your ad campaign in March.

Here's another example: Suppose that the primary objective of a marketing campaign is to increase brand awareness. Or to establish your company's credentials as a thought leader in your industry. Those aren't exactly goals that you can measure with simple arithmetic. Yet, they may be vital to your business's long-term growth. Again, ROAS won't be able to measure your campaign's performance with a lot of accuracy.

With that in mind, let's dig a little deeper into two important aspects of marketing that ROAS can't quite handle:

The "halo effect" refers to a customer's "favouritism toward a line of products due to positive experiences with other products" from the company. In other words, when a customer is pleased with a particular purchase from your business or enjoys a pleasant experience with your brand, they are more likely to buy other products from you, even if those products have nothing to do with their original purchase.

Once again, ROAS isn't able to account for the halo effect across different product categories. For example, imagine that a customer purchased a coffee-maker from an online company. Their shopping experience was easy, the shipping was fast, and the coffee-maker works great. Several months later, the customer buys a TV from the same company. That second purchase may not show up on any ROAS calculations, but it's directly correlated to the customer's positive experience. (And unless they bought a really expensive coffee-maker, their second purchase is far more valuable to the company than the first!)

A lot of executives love ROAS because it provides a snapshot of immediate returns from a specific marketing campaign. For instance, a lot of CFOs use return on ad spend as a key component of budget development. And, indeed, a high ROAS often means that the business' advertising strategy is performing well.

Of course, the downside of relying exclusively on ROAS to make key marketing decisions is that you may be missing the bigger picture. Marketing does more than generate profits in the short term. A solid marketing strategy should also build lasting value, and drive profits for months, perhaps years to come.

The key here is to remember that marketing expenses (including ad spend) should build your brand as an asset for the future. If an ad

• makes a customer aware of your company's existence
• makes a customer identify with your brand more closely
• or makes a customer more knowledgeable about your products

then it may not matter if the customer buys from you today, or even several weeks from now. As long as the customer buys eventually, the ad has accomplished its purpose. That's why ROAS should only be one piece of the puzzle when it comes to measuring campaign performance.

Put simply, marketing efficiency ratio is total (not just immediate, but total) revenue divided by total ad spend from all marketing channels. MER allows you to take a step back, so to speak, and look at the cumulative effects of your marketing efforts over time. This metric also empowers you to make more strategic business decisions, and not to quickly react to "problems" with your marketing plan (like your ROAS dropping from $5 to $4.50).

MER can help you to see the interconnected value of all of your marketing assets. It measures how efficiently those assets, both individually and collectively, generate revenue for your brand. For instance, SEO-driven content provides a classic example of how assets can continue to deliver value long after the company's initial investment in them. It may cost some money upfront to develop a blog, and possibly hire a copywriter — but that blog may still be moving buyers through the sales funnel for years thereafter.