There are many who see a slow recovery in U.S. ad spending.

Then there are the pessimists at PricewaterhouseCoopers who not only don't see a recovery soon but actually think ad spending will continue sinking, such that by 2013 it will be below where it was last year, at $174 billion versus $189 billion.

That’s a decline of 1.7 percent per year. Global spending will sink even more.

That's grim stuff, and the reason is less about the economic recession than a continuing and indeed accelerating shift to targeted digital media and away from less-efficient mass media that has been the mainstream of American advertising in modern times.

Further, ad spending may not ever return to earlier levels, warn the authors of PwC's Global Entertainment and Media Outlook: 2009-2013, which is out this morning.

The report describes a profound structural shift to more efficient digital ad models, and it warns, "This in turn may result in a permanent reduction in total advertising spend, as dollars formerly ‘wasted’ through inaccurate targeting are saved and reallocated to other priorities."

Most vulnerable, as one would expect, are newspapers and magazines but also television, which so far has fared far better than print media.

The internet will continue to grow as an ad medium, according to the report. The internet's share of total U.S. ad revenue will rise to 19 percent in 2013 from 13 percent in 2008.

Overall U.S. spending on entertainment and media, which includes advertising but also consumer spending, will see a modest 1.2 percent growth on average through 2013, to $495 billion in 2013.

Right up there will be the internet, both advertising revenue and access fees. Other gainers include video games, movies and other filmed entertainment, and TV subscriptions and license fees.

Globally, entertainment and media spending will grow at an annually compounded rate of 2.7 percent through 2013, to $1.6 trillion, according to the report.