Campaign metrics: Why you shouldn’t rely on this single indicator for success

Advertising drives results that matter for your business but aren’t captured by ACOS. The advertising cost of sales metric helps you quickly assess how cost-effective your ad campaigns are in generating immediate sales. But immediate sales and high return on investment (ROI) are not the only indicators of success.

A campaign with higher ACOS, for example, may potentially be better at driving action higher in the marketing funnel—for example, generating new customers, subscriptions, or detail page views—than a campaign with lower ACOS. These outcomes drive awareness and consideration and could ultimately help your business achieve more long-term success. While ACOS is a valuable metric, using it as the only proxy for success will cause you to miss the bigger picture.

Are you launching a new product and need traction? Consider focusing on overall sales instead.
Are you trying to increase customer loyalty? Look at subscriptions.
Does your product page have a high conversion rate but not receive enough traffic? Consider using clicks or detail page views as your KPIs.

Comparing campaigns by ACOS alone assumes that all else is equal. But in reality, campaign results can be shaped by any number of factors. Particulars such as the advertising goal (customer acquisition versus retention), product lifecycle stage (new launch versus growth), keyword competitiveness, product price, and even ad creative can vary between campaigns and impact ACOS differently. Furthermore, the appropriate trade-off between ACOS and sales will change depending on your campaign goals.

For example, ACOS tends to be lower for remarketing campaigns, your best-selling products, or branded keywords, but higher for prospecting campaigns, new products, or highly competitive keywords.¹ Concluding that one campaign performed better than another simply because it had a lower ACOS ignores the strategic and tactical differences that may have directly impacted ACOS in the first place.

Different campaigns can complement each other to deliver better results, and activity from one campaign can affect the ACOS of a different campaign. For example, consider the following scenarios where your brand has two separate campaigns running at the same time:

In scenario one, you have:

• A display ads campaign that generates few sales but drives new branded keyword searches (high ACOS)
• A sponsored ads campaign that targets those keywords and, in turn, succeeds in driving sales on Amazon (low ACOS)

In scenario two, you have:

• A sponsored ads campaign that drives few sales on Amazon but a high volume of detail page visits (high ACOS)
• A display ads remarketing campaign that successfully brings those customers back to complete a purchase (low ACOS)

Brands such as Seiko, Rhodius, and WaterWipes, for example, have seen positive results in conjunction with similar strategies. After complementing their sponsored ads campaigns with display and broadening their advertising goals beyond ACOS, each saw more than double the volume of earned media and branded keyword searches during the campaign period—in two cases even lowering their overall ACOS.²

Even if ACOS is your primary KPI, it is misleading to compare the ACOS of new campaigns to the ACOS of existing campaigns. The law of diminishing returns says that as you put more dollars into an investment, the returns will eventually decrease. But this does not necessarily mean that you should stop investing once you reach that point. If your return is still positive and higher than what you could achieve elsewhere (your opportunity cost), it makes sense to keep investing.

In the case of advertising, this means you should not necessarily stop spending if you notice your ACOS dips below a previous benchmark. The question is not What has my ACOS been up until now? but rather What is the best return I can achieve with one more dollar?

For example, if you put your entire budget into a sponsored ads campaign, you may eventually hit the ceiling of the audience whose shopping queries match your product. At that point, prospecting—that is, reaching audiences who are not relying on shopping queries—may be a more cost-effective tactic.

Ultimately, ACOS is just one of many metrics to help guide your decision-making. Effective advertising is a holistic effort. You should seek to reach audiences at multiple touch points, and use complementary strategies through multiple channels can help achieve a range of goals, short-term and long-term. By looking at ACOS alongside other metrics that support the long-term growth of your business, you can achieve a more complete perspective on the success of your campaigns.

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