According to WPP’s GroupM, advertisers are wise to pay attention to outdoor, radio and print-based media.

In a blog post, GroupM analyst Brian Wieser writes that “outdoor, radio and print-based media rarely see the focus that pure-play digital and television-related media do, but continue to offer significant opportunities for marketers.”

Thanks to investments in digital infrastructure, outdoor advertising is growing faster than all other channels except pure-play digital. Wieser says that outdoor advertising’s “effectiveness is relatively undiminished by fragmentation or ad avoidance, at least where related real estate is constrained by local laws and regulations” and points out that savvy marketers are seeing it as “a superior alternative to television when goals are focused around brand-building and target audiences are in geographically narrow areas.”

Radio, while not growing as fast as outdoor, has also seen major investments in digital infrastructure and offers wide reach that advertisers willing to see past its historic reputation can tap into. Print, while still a shadow of its former self as a result of significant circulation declines, is a viable niche channel that can be highly-effective, Wieser suggests.

All told, GroupM predicts that in 2020, outdoor, radio and print will account for 3.5%, 6.6% and 9% of US ad spend, respectively. Individually, these percentages pale in comparison to television and digital, which the agency expects to account for 28.5% and 52.5% of ad spend, respectively, but when combined, these channels make up a fifth of the market.

There are a number of reasons that figure could increase in the coming years.

First, many of the most attractive features of pure-play digital advertising have been brought to outdoor, radio and print. For instance, it’s now possible for advertisers to purchase inventory in these channels much the same way digital inventory is purchased. Targeting and tracking capabilities are often close to or on par with digital channels, and some traditional channels now even have programmatic offerings. As such, it’s easier and more cost-effective for advertisers to create, manage and scale their campaigns.

Second, for all of digital advertising’s virtues, it has limits and some advertisers are running into them. Once they have picked the low-hanging fruit, especially with the two biggest digital ad players, Google and Facebook, a growing number of marketers are deciding it makes more sense to allocate spend to less competitive channels than to accept diminishing returns from digital. This trend is especially strong among direct-to-consumer (D2C) brands.

Going forward, it’s all but certain the appeal of traditional channels will only grow, even if competition increases. That’s because the amount of quality traditional inventory that will become readily available as media sellers build out digital infrastructure is likely to grow. Additionally, advertisers will increasingly have to grapple with a changing digital advertising landscape that won’t look quite the same thanks to government regulation, industry self-regulation and the crackdown on cookies.