From Annelena Lobb:
Brazil edged past China to become the largest emerging market in the world, as measured by Morgan Stanley Capital International's emerging markets index. Brazil has a free-float market capitalization of $509.10 billion and comprises 14.95% of the index; China, $481.80 billion and 14.15%, respectively, according to MSCI, FactSet and Citi Investment Research.
I suspect this is a function of the fact that many Chinese companies have only sold off a relatively small portion of their capital in the public markets, while big Brazilian companies like Vale and Petrobras have had multiple rounds of equity offerings. But even so, it's impressive, given that the Chinese stock market is in a bubble phase while the Bovespa isn't.
See also: Brazil Takes Emerging Market Crown