Asia's largest furniture exporter Samson Holding has boosted the size of its initial public offering by 15 per cent to $2.18 billion after exercising the overallotment option in full - after only three days of trading. The news means that bookrunner Morgan Stanley has forfeited the flexibility of using the additional shares to stabilise the stock should it fall below the issue price over the next couple of weeks and shows the investment bank is confident that there will be enough institutional demand to support the price. An overallotment option is usually valid for 30 days and typically, the bookrunners will not exercise it until at least half of that time has lapsed, allowing them to prop up the price by buying back the overallocated shares should things take a turn for the worse. The exercise of the overallotment option also highlights that poor demand from retail investors is not necessarily an indication of weak demand overall. Samson said last week that its 10 per cent retail tranche had been only 21.87 per cent covered and the remaining shares would be reallocated to institutional investors. It priced its offering at $2.75, towards the low end of the $2.60 to $3.25 range. Since its trading debut on Thursday, the price has risen 7.27 per cent to yesterday's close of $2.95, while the Hang Seng Index has edged up 1.6 per cent. At the time of listing, sources said there were some institutional investors lining up to buy the stock in the secondary market. Following the exercise of the overallotment option, 28.7 per cent of Samson's shares will be in public hands, compared with 25 per cent at the time of listing. Separately, sources said the institutional tranche of Dongfeng Motor Group's up to $4.58 billion global share offering had received more orders than shares offered. The retail offer will start tomorrow.