Stocks traded, total value (% of GDP) [Source: World Bank]: http://data.worldbank.org/indicator/CM.MKT.TRAD.GD.ZS
Market Capitalisation of the World's Top Stock Exchanges (As at end Sep 2015) [Source: HKSFC]: http://www.sfc.hk/web/EN/files/SOM/MarketStatistics/a01.pdf
Hope the links help. :)