The Mekko chart/Marimekko chart below shows valuations of large startups across different verticals. Each vertical is defined as a column with the width proportional to the sum of the values of all the startups in the vertical. Each segment is a startup with its area proportional to valuation.
Uber has the largest valuation at $51B closely followed by Xiaomi valued at $46B. This data is from Wall Street Journal and valid as of November 2015. Excludes startups that have gone public.