The size of the advertising market is difficult to assess, and estimates by analysts vary to some degree. The final cost of advertising for any company includes creative and agency costs; local branding and marketing efforts; catalogs, brochures and other printed matter; the creation and maintenance of web sites and myriad other components, in addition to expenses for media. Numbers that are available for analysis and comparison are generally limited to actual spending on media, such as radio, TV, billboards and paid search or Internet advertising. Even these numbers are often educated guesses.

Estimates of ad spending may include spending at both local and national media outlets, as well as spending on Internet media via paid search and online ads. By all accounts, the recent global recession took an immense toll on the industry, as revenues declined and layoffs were announced, from agencies to broadcasters to magazine and newspaper publishers. Many well-known magazines closed down, and a handful of respected newspapers went to online only versions. Many advertisers were unable to pay their bills. GM alone owed more than $100 million in advertising bills as it entered bankruptcy.

The advertising industry enjoyed a rebound in 2010, as significant economic growth boosted emerging nations, and the U.S. and other mature nations found themselves on firmer ground. Analysts at GroupM estimated global advertising spending at $474 billion in 2010, up about 5% from 2009.

Analysts at Magna project U.S. advertising revenues at $171 billion for 2011, up a modest 3.1% over 2010. Among the many reasons for little growth in American ad spending is the fact that ad rates have been very soft. Media firms in many cases have been forced to make generous deals in order to attract scarce ad dollars. This situation will eventually improve as the economy recovers and advertisers are more optimistic. On a more positive note, advertising spending is forecast to have outstanding growth in emerging markets such as China, Malaysia, Argentina and Brazil.

Among the best growth areas in advertising in recent years have been advertising on mobile devices, which is still in its infancy, advertising on movie screens and advertising online. Analysts at Gartner expect mobile advertising to reach $13 billion worldwide by 2013. Magna forecasts that global online advertising, including search, will grow to $71 billion in 2011.

Advertising is irrevocably linked to media, whether traditional media like the 14,741 broadcast radio stations in America (about $17.3 billion in annual revenues), commercial and educational broadcast TV stations plus myriad cable and satellite TV outlets (totaling about $50 billion in advertising revenues), the 2,298 daily and Sunday newspapers (about $22.8 billion in annual print advertising revenues) or new media like the tens of thousands of Internet sites that now accept advertising. The advertising sector also includes direct mail, at about $19 billion yearly in the U.S.; magazines, at about $15 billion in revenues; and outdoor advertising, at about $6 billion. In addition, there is significant activity in specialty and alternative advertising, everything from ballpoint pens printed with a message to t-shirts to small airplanes towing advertising banners. Branding, marketing and public relations activities and services generate billions more in revenues.

Advertisers are faced with daunting new realities when considering the various media they might use to get their messages across. Traditional media are losing control over their audiences. That means that advertisers can no longer feel secure that their ads on TV, on the radio or in print are going to receive mindshare. Gone are the days when television and radio programmers enjoyed captive audiences who happily sat through ad after ad, or planned their schedules around favorite shows. Consumers, especially consumers in younger demographics, now demand more and more control over what they watch, read and listen to, and thus more control over the advertising they might be exposed to.