The economic slowdown in the U.S. hasn’t spared the advertising industry, with multiple forecasts anticipating that ad spending will dip even further this year and take yet another tumble in 2009.

The situation has slowed growth in digital out-of-home spending as well, but the segment remains healthy and is still expected to grow by double digits this year versus last.

The U.S. digital out-of-home media industry is on pace to grow 11.2 percent to $2.43 billion in 2008, according to a report released this week by PQ Media. That’s about on par with global growth in the digital out-of-home market, which PQ says will be up about 12.8 percent to $6.11 billion.

That's dramatically below the pace of 2007, when digital out-of-home grew 24.5 percent over 2006 here in the U.S. and 22.6 percent worldwide.

PQ expects growth to slow again in 2009, but still forecasts ad spending in the U.S. to grow at a compound annual rate of 12.9 percent from 2007 to 2012 and 14.5 percent worldwide.

PQ includes video advertising networks and digital billboards in its definition of digital out-of-home media.

PQ's forecast is backed up for new data on shipment of digital signage displays. The number of units shipped this year has reached 1.1 million, up 34 percent from last year, according to MultiMedia Intelligence, a market research firm based in Scottsdale, Ariz. That number is expected to more than double by 2012, to 2.3 million displays.