The Singapore Exchange (SGX) has proposed changes to its listing rules that ask for at least 5 percent of the shares to be given to retail investors in a mainboard listing, a local newspaper reported on Monday. The changes are aimed to increase retail investor participation so as to "enhance the vibrancy of trading in the secondary market, leading to greater liquidity and potentially improved valuations for listed companies," the SGX said. It is also proposing the introduction of a claw-back mechanism that increases the number of shares allocated to the public subscription tranche when the total demand for shares in the tranche exceeds prescribed thresholds, the Straits Times reported. When the demand through public subscription is below the prescribed thresholds, a reverse claw-back mechanism can be introduced to transfer shares from the public subscription tranche to the placement tranche meant for institutional investors. The SGX had first raised the idea of lifting the proportion of shares allocated to retail investors in July. In a popular IPO earlier this year, only 2 percent of the IPO shares sold by IHH Healthcare in its July debut were meant for Singapore retail investors, and were 11 times oversubscribed. The SGX said in July that 76 percent of the 90 most recent IPOs had offered less than 5 percent of shares to small investors.