Telecoms group MTN added 4.1million more users to its books in the quarter ended March, taking its total user base to 227.5million subscribers. Data revenue increased by 16.7% in the quarter, when compared to the first quarter last year, the company said yesterday.Data now contribute 21% of the group's revenue, said MTN, which continued to expand its 3G and LTE networks during the period.Weaker economic environments in the company's two major markets, Nigeria and South Africa, negatively affected the quarterly results, it said.The price of oil, the biggest economic driver in Nigeria, halved last year, reducing the economic growth of Africa's biggest single economy.In South Africa, the economy grew at 1.5% last year, eroding the disposable income of cellphone users.WhereMTN's 24million local subscribers spent on average R95.21 on their cellphones in the first quarter last year, the 28million users it now has on its books spent on average R87.16 in the quarter to March.In Nigeria, the 57.2million people that used MTN's cellphone services last year spent on average 1177.82 naira (about R72), while the 61.1million people now spend on average 1102.59 naira.Measured in US dollars, MTN Nigeria's average revenue per user declined from $7.21 during last year's first quarter to $5.68 this first quarter.South Africa's average revenue per MTN user also fell by $2 to $7.45 this year.The company has maintained its target of adding 17.5million customers this year...