GSM-based mobile operators have been celebrating as they have collectively added 8.3 million subscribers last month. The final count was 306.4 million GSM subscribers which was a significant growth compared to 298.1 million in April. Bharati Airtel tops the charts in the GSM listing with 32.48% of market share. 

Here is a comparative chart of other players:
Network                    Addition            Total Subscriber Base
Vodafone Essar 2.5 million            74 million
Idea Cellular 1.3 million            45.4 million
BSNL 4.5 lakh                  48.1 million
MTNL 38,036 lakh         4.2 million

But May was not a good month for BSNL. The service provider could not keep up with the 1 million new users it acquired in April.