The average annual income of farmers in West Bengal has tripled during the past eight years of Trinamool Congress(TMC) rule, Chief Minister Mamata Banerjee said on Monday. Paying her tribute to former prime minister and farmers' leader Chaudhary Charan Singh on his birth anniversary, Banerjee, who is also the TMC boss, said distribution of Kisan Credit Cards has increased 2.5 times over this period.