The De Beers Group said Friday that total sales increased 26 percent year-over-year to $7.4 billion. Sales of rough diamonds by the Diamond Trading Company, the company?s the rough diamond sales and distribution arm, increased 27 percent for the year to $6.5 billion?the second highest level of sales for the diamond giant. Diamond prices for 2011 rose 29 percent as diamond production fell 5 percent to 31.3 million carats, compared with 2010.