A surprise dividend cut from Aviva meant that the life insurance sector was the worst performing category on Thursday as shares in the UK firm plummeted.The stock was down 11.6% at 318p in afternoon trade after the company swung to a loss after tax of £3.05bn in 2012, compared with a profit of £60m the year before, as it took a £3.3bn write-down on the disposal of its US operations.As such, the final dividend per share (DPS) was cut from 16p to 9.0p, bringing the full-year DPS to 19p, down from 26p previously, in an effort to "reduce leverage and increase retained earnings". Aviva also decided not to pay bonuses for executive directors for 2012 or pay rises for 2013.Sector peer Standard Life was also under the weather today despite beating forecasts with its full-year results, underwhelming the market with a special dividend worth £302m.Shares were 0.4% lower at 372.7p but have still risen around 13% in 2013 so far, following a massive 58% jump in 2012.Insurance stocks Phoenix, Legal & General, Old Mutual and Resolution were also lower today.Top performing sectors so far todayHousehold Goods & Home Construction 9,769.80 +1.63%Industrial Engineering 9,758.21 +1.28%Chemicals 9,512.30 +1.22%Food Producers & Processors 7,350.16 +1.22%Support Services 5,975.94 +1.16%Bottom performing sectors so far todayLife Insurance 5,604.73 -1.70%Technology Hardware & Equipment 1,142.42 -1.15%Mobile Telecommunications 4,162.48 -1.04%Fixed Line Telecommunications 3,108.23 -0.91%Automobiles & Parts 6,619.06 -0.67%BC