Group M has revisited and dropped its original 2011 ad spend forecast from 5.8% to 4.8%. This decrease is due to devastating natural disasters, like those in Japan earlier this year and the political turmoil in the Middle East.

The revised spending forecast, which appears in GroupM’s biannual report, “This Year, Next Year,” predicts that global ad spend will hit $506 billion in 2011, a 4.8% increase over 2010.

Ad spending in North America is expected to grow 4% over 2010 numbers in 2011 and remain steady in 2012.

Growth is forecasting growth in all areas of the Canadian media landscape in 2011, with the exception of business magazines, which the company reports will see a drop of 3%. Consumer magazines are expected to stay flat for the year.

Pay TV is expected to see the largest year over year change from 2010 to 2011, with a 10% jump. Free to air TV will see a 5% boost in Canada, according to the report.  Radio is expected to see a 3% boost in 2011, newspapers a 4.5% jump, cinema sees a 4.8% increase and OOH is forecasted to see a 6.1% boost in ad spending  this year.

A global ad spend increase of 6.8% is expected in 2012, fuelled by the London summer Olympics and the US  Presidential campaign that year.

Digital also continues to gain speed in this year’s report, accounting for 17% of global advertising in 2011, a full point ahead of the previous forecast done in December 2010.

The “This Year, Next Year” report is part of GroupM’s media and marketing forecast drawn from data supplied by parent company WPP.