In 1995, helical CFLs, manufactured in China by Shanghai Xiangshan, became commercially available. They were first proposed by General Electric, who saw difficulties bending glass tubes into spirals using automated machinery. Xiangshan solved this problem by bending the tubes by hand, made possible by the then-low labor costs in China. Since that time, sales steadily increased. The phosphor coating in spiral CFLs is uneven, being thicker at the bottom than at the top, owing to the effect of gravity during the coating process. Although their popularity varied across countries, in China CFLs were the "dominant technology in the residential segment" in 2011.