UPDATE 1-Account wins help ad group WPP secure strong end to 2015
(Adds details) LONDON, March 4 (Reuters) - Strong growth in North America and a spate of major account wins helped WPP, the world's biggest advertising company, to end 2015 with the best growth of the year and start 2016 on a solid footing. The last major ad group to report 2015 resul
