LAGOS (Reuters) - Ecobank posted a 47.4 percent jump in half year pretax profit to 61.41 billion naira ($309 million) versus the same period a year ago, the Pan-African banking group said on Thursday. Ecobank said gross earnings climbed to 211.32 billion naira in the period to end-June from 175.05 billion naira a year ago. "We continued to drive cost efficiencies in our businesses and our cost-income ratio improved to 62.5 percent compared to 68.1 percent in the previous year," Albert Essien, Ecobank's chief executive officer said in a statement. ($1 = 198.9800 naira)