of eleven states began pursuing the idea of utilizing enhanced co-operation to implement the tax in states which wish to participate. Opinion polls indicate that two-thirds of British people are in favour of some forms of FTT (see section: Public opinion). The proposal supported by the eleven EU member states, was approved in the European Parliament in December 2012, and by the Council of the European Union in January 2013. The formal agreement on the details of the EU FTT still need to be decided upon and approved by the European Parliament. Evaluation Effect on volatility Proponents of the tax assert that it will reduce price volatility. In a 1984 paper, Lawrence Summers and Victoria Summers argued, "Such a tax would have the beneficial effects of curbing instability introduced by speculation, reducing the diversion of resources into the financial sector of the economy, and lengthening the horizons of corporate managers." It is further believed that FTTs "should reduce volatility by reducing the number of noise traders". However most empirical studies find that the relationship between FTT and short-term price volatility is ambiguous and that "higher transaction costs are associated with more, rather than less, volatility". A 2003 IMF Staff Paper by Karl Habermeier and Andrei Kirilenko found that FTTs are "positively related to increased volatility and lower volume". A study of the Shanghai and Shenzhen stock exchanges says the FTT created significant increases in volatility because it "would influence not only noise traders, but also those informed traders who play the role of decreasing volatility in the stock market." A French study of 6,774 daily realized volatility measurements for 4.7 million trades in a four-year period of index stocks trading in the Paris Bourse from 1995 to 1999 reached the same conclusion "that higher transaction costs increase stock return volatility". The French study concluded that these volatility measures "are likely to underestimate the destabilizing role of security transactions since they – unlike large ticks – also reduce the stabilizing liquidity supply". A 1997 study of the UK Stamp Duty, which exempts market makers and large banks that are members of a qualifying exchange, found no significant effect on the volatility of UK equity prices. Effect on liquidity In 2011 the IMF published a study paper, which argues that a securities transaction tax (STT) "reduces trading volume, it may decrease liquidity or, equivalently, may increase the price impact of trades, which