After six years of hovering between $20 billion and $22 billion, 2009 TV industry revenue will take a dramatic fall below the $20 billion mark starting this year, reports MediaBuyerPlanner.

TV industry revenue for 2009 is expected to end at an even $17 billion , a 21.2% drop from 2007’s $21.5 billion, according to a forecast from BIA Advisory Services, LLC.

BIA is predicting a slight revenue increase of .6% in 2010, because of an election year and a recovering economy, but expects that 2011 will likely see a small dip into the negatives again. It won’t be until 2012 that the TV industry will see a solid return to positive revenue streams. In 2012, BIA expects an additional $1.1 billion in ad revenues will come to local television stations from providing mobile video programming to cellular, mobile, and portable handsets.

BIA reported that TV revenue declined just 6.6% in 2008, but that number would have been lower had fierce presidential and congressional campaigns not been held in battleground states.

“Transformation” is the only path to expansion for the industry, BIA said, predicting that dramatic changes will come from cross-platform growth, along with “real energies put into finding local advertising revenues available through mobile and online advertising.”

Another company forecast, from Zenith Optimedia, predicts that TV ad expenditures will fall 5.5% in 2009, while TV’s share of the market will grow from 38.1% in 2008 to 38.6% this year.