The notion that together search and display advertising can be greater than the sum of their parts is nothing new. But when it comes to actually making them greater than the sum of their parts in the real world, large marketers are apparently having some trouble.

That’s what Forrester Consulting found in a study that was published yesterday.

According to the study, despite the fact that the majority of marketers surveyed devote more than 50% of their spend to search and display, over half (60%) still rely on spreadsheets — yes, spreadsheets — to manage search and display campaigns together.

Given that figure, it’s probably no surprise that many marketers are finding it difficult to measure the combined results of their search and display campaigns. In fact, Forrester found that not being able to track combined results is the most frequently cited barrier to effective campaign management. Without measurement of course, it’s hard for marketers to allocate resources effectively to maximize ROI.

So what are marketers to do? Forrester suggests that technology is the answer, and that sophisticated ad management platforms are going to play a big role. It should, of course, be noted that Forrester’s study was sponsored by Efficient Frontier, which offers such a platform. But ad management platforms that seek to allow marketers to manage multiple channels are becoming more prevalent in the marketplace for good reason: the marketplace is more sophisticated.

Marketers realize that search, display, email and social don’t work best when they’re treated like silos, but you can’t break out of silos by sheer will alone. To succeed with cross-channel campaigns, you need cross-channel tools.

The good news for marketers is that digital advertising channels are already some of the most effective around, even if marketers aren’t yet integrating management of their digital channels as well as they could be integrated. As the tools that enable marketers to analyze and manage multiple digital channels become more widely-used and robust, digital advertising campaigns should only become more effective.