What is the fine-grained topic of the following text: According to new industry data from the Communications Authority of Kenya (CAK), Airtel, part of India’s Bharti Airtel, the third largest mobile carrier in the world, lost 7.8% of its subscribers in the first quarter of this year, compared with the previous quarter, while its rival Safaricom, partly owned by the UK’s Vodafone, saw a 2.7% increase. Only return the topic.
Kenyan telecommunications industry performance data