Heavy TV viewers -- those watching almost 12 hours a day of TV -- contribute almost half of all TV viewing. And for marketers this isn’t such a bad story.A recent study from Nielsen says heavy viewers -- the biggest of five equally sized groups of viewers -- earned the top spot in 10 out of 17 purchasing categories including automotive, apparel, electronics and dining purchases. Heavy TV viewers are 16% more likely to buy a domestic car and 17% more likely to have purchased new clothing in the past year.These major consumers of TV content are still increasing -- up 8% over the last five years. Nielsen says that’s an increase of almost one hour a day of TV viewing.Heavy TV watchers consume 705 minutes a day of TV. Nielsen says African-Americans are 75% more likely to be heavy television viewers, tuning in for an average of 917 minutes per day.The second-biggest TV viewing group comes in at a little more than 6 hours a day or 362 minutes, representing 24.9% of overall TV viewing. The next group pulled in over three-and-a-quarter hours a day, at 227 minutes. It has a 15.5% share.The lighter TV viewers group -- those watching a little more than 2 hours a day, at 127 minutes -- have a 8.6% share. The lightest TV viewer group takes in just a little more than a half hour of TV time per day at 35 minutes, and has a 2.4% share.