2017 has been the year that advertisers called out digital advertising as broken and sorely in need of repair. As stewards of the investment that funds the internet, these ad execs should be applauded for their insistence on better performance. That said, their focus has been on surface issues related to the ad experience, while a larger problem lies beneath.

These surface issues are what we refer to at Nielsen as “hygiene” because they contribute to campaign waste but can be cleaned up by applying an aligned set of rules. For example, once advertisers, agencies and publishers align on a definition of “viewable,” impressions which don’t meet the standard will no longer be counted. Likewise for “fraud/invalid traffic” and “brand safety.”

Today these obstacles are certainly making the waters murky; advertisers may be losing 60% of their digital ad campaign impressions. Once they are resolved, however, these impressions will no longer count and the surface will clear.

At that point, however, the real danger lying beneath the surface will come to light: the under-delivery of intended audiences. This is back to fundamentals; advertisers need assurance that their campaign is delivered to the audience they bought, which requires post-delivery validation. By way of example, across digital campaigns targeted to the TV currency demo (persons 18-49), Nielsen sees on average only a 68% delivery on target, a number which only decreases as you shrink the target to be more precise.

A target of females 18-34, for example, typically results in 23% delivery on target. In the linear television world, we now see campaigns bought on an audience basis using data from combinations of set top boxes and third party marketing companies; our research estimates that such campaigns are likely to deliver half of impressions outside of the demo.

Now imagine that you have a $5 million cross-media campaign, with 40% ($2 million) allocated to digital and the balance to TV. Of that digital portion, hygiene issues create on average $1.2 million of waste. Of the $800,000 remaining, 32% of that misses the intended audience, leaving only $544,000 of the original $2 million digital allocation working for you.

Fix the hygiene issues and the problem of audience delivery just grows. In other words, if 100% of my $2 million digital spend in view, the audience on-target percent becomes the bigger problem. It still remains that only on average 68% of the broadest target will be seen by the intended audience. Some may insist that at least it’s seen by a person, and therefore has some value, but remember that this is not the deal—this is not what was bought. Knowing this and validating the buy is critical.

Advertiser calls for MRC accreditation of digital walled garden metrics are well meaning, but do not go far enough. Data received from separate publishers do not necessarily use the same definitions and crediting rules and are therefore not comparable. They are also not comparable to the data coming from the linear TV platforms, nor to the linear TV ratings.

What is really needed here is truly independent, third party measurement of the entire marketplace on a like-for-like basis. This is the core of audience measurement—standardized, comparable, independent data with a full-market view enabling transparency and transactions, so advertisers get what they pay for.

This article originally appeared on WARC.