* Stock market investors bid up rates to raise cash
* Little impact on wider money market seen
* Investors like IPOs for outperformance over indexes
* Regulators set to approve around 100 listings this year
By Pete Sweeney
SHANGHAI, June 19 (Reuters) - Chinese investors hungry for cash to buy into upcoming initial public offerings have turned to little-known overnight pledged bond repurchase (repo) agreements for funds - driving up the cost of borrowing nearly four-fold for the week, with the cost of borrowing for 24 hours as high as 16 percent on Thursday.
"The main reason behind the performance of pledged repo rates in the Shanghai Stock Exchange is the restarting of IPOs, with both retail and institutional investors showing great enthusiasm for participation," said a trader from a state-owned bank in Beijing.
Other commonly-traded instruments such as seven- and 14-day pledged repo contracts have posted similar rises over recent days.
Pledged repos are a derivative fundraising tool used in China's stock exchanges to raise funds for quick transactions, and the market has received scant attention until recently.
A pledged repo transaction involves a customer pledging bond assets they own as collateral to the repo issuer, which advances cash at a certain interest rate for short periods.
Historically the pledged repo market has proven far more volatile than the primary interbank money markets.
The rise in pledged rates, however, has not trickled into the much larger interbank market, where benchmark instruments have yet to show signs of pressure, and traders do not expect them to do so in the future.
The weighted average of the benchmark seven-day repo rate stood at 3.12 percent on Thursday, up slightly from Wednesday but well within accommodative territory.
The interbank bond market, dominated by banks and big institutional investors, dwarfs those on the Shanghai and Shenzhen exchanges which are more focused on retail investors.
Beijing allowed IPOs to resume in early 2014 after over a year-long hiatus, letting nearly 50 previously-approved companies list.
Those new issues performed strongly, up by an average of 70 percent from their IPO prices since listing in January and February, according to Reuters calculations.
In comparison, the CSI300 index, which tracks the largest firms trading in Shanghai and Shenzhen, is down nearly 6 percent in the year to date.
Four companies have priced their IPOs so far, aiming to raise up to 1.7 billion yuan ($274 million), with listings expected soon.
But the total amount of funds raised looks set to fall short of original expectations. The China Securities Regulatory Commission (CSC) has said it intends to allow 100 companies to list, about half of the number projected by analysts.
While that is bad news for underwriters and investment banks, it is positive for liquidity sentiment.
Massive IPO surges can put pressure on money markets, and in China they also tend to dilute the net valuation of shares in the market as investors close out positions in already-listed companies in order to buy new listings. ($1 = 6.2090 Chinese Yuan) (Additional reporting by the Shanghai Newsroom; Editing by Eric Meijer)