(Telecompaper) MTN Group posted a 12 percent increase in its revenue for 2013 to ZAR 136 billion compared with 2012, boosted by a weakening of the rand against a number of currencies. For the year as a whole, the rand declined by 18.3 percent on average against the US dollar. On a constant currency basis, revenue increased by 3.1 percent. This was largely the result of a 6.1 percent decline in revenue at MTN South Africa and 5.7 percent growth in MTN Nigeria.