In an effort to help some companies battered by extreme market volatility in recent months avoid delisting, the New York Stock Exchange announced a plan to temporarily lower the average market capitalization required of its listed companies from $25 million to $15 million.

The temporary reduction, announced in a Jan. 23 press release, will apply through April 22, 2009.

The move by NYSE follows a rule filing by NASDAQ to temporarily suspend its bid price and market value of publicly held shares through April 19, 2009.

Section 802.01B in the Exchange’s Listed Company Manual requires prompt delisting of any company that has an average global market capitalization over a consecutive 30 trading-day period of less than $25 million. However, in the past several months, NYSE noted that the number of listed companies whose average global market capitalization has fallen below $25 million over a 30 trading-day period has been “significantly higher than the historical norm.”

“The Exchange believes that, in many cases, these companies have experienced precipitous stock price declines because of these unusual market conditions, rather than company-specific problems,” the rule proposal filed with the Securities and Exchange Commission states.

The rule filing is immediately effective, but is subject to a 30-day operative delay under SEC rules. NYSE asked the SEC to waive the delay so the change would take effect upon filing.