Find your company’s stock plunging these days? Try a buyback.

At least a dozen L.A.-based firms have joined the increasing number of public companies nationwide that are buying back their own shares on the open market.

“I haven’t seen this amount of buybacks in the 11 years I’ve been in the business,” said Bryant Riley, president of B. Riley & Co., a Santa Monica-based brokerage house. “It seems like every company has some kind of a buyback in place.”

Buying back shares is a popular way for companies to boost their stock price and possibly set the groundwork for raising money through future stock offerings. Typically, a company will buy the shares and retire them, thereby reducing the number of shares in circulation. That, in turn, increases the company’s earnings per share and, in theory, boosts its share price.

Buybacks typically are seen as a positive sign, as they indicate that management remains confident about the company’s future performance so much so that it is willing to risk money on its stock.

“Judging by their actions, companies have turned very bullish,” said Charles Biderman, president of Trim Tabs Financial Services, a Santa Rosa-based research firm that tracks stock market liquidity. “It is a good sign that the economy is not going to fall out of bed.”

The biggest of the recent local buybacks is being undertaken by Reliance Steel & Aluminum Co. On Aug. 31 the company said it would expand its repurchase program by 2.5 million shares, to a total of 4 million.

With Reliance’s stock trading at about $32 last week, the expansion represents an additional $80 million investment by the company, bringing the total value of the buyback to around $128 million.

Imperial Bancorp, parent of Imperial Bank, announced earlier this month that it would resume its buyback program, taking up to 1.65 million shares out of the market. Imperial’s stock was trading at the $20 level last week, for a total cost of at least $31 million.

“When the share price goes down to these levels, the best thing we can do for our shareholders is to buy back stocks,” said Norman Creighton, Imperial’s president. “If the shares continue to trade at this range we expect to complete the entire buyback.”

That, however, could take weeks, if not months. Imperial, like all other public companies, must limit its daily purchases to 25 percent of the entire trading volume for the stock in the previous week.

Creighton said the bank had already completed around 30 percent of the buyback. So with around 70,000 Imperial shares traded in an average week, it would take at least 14 days of continuous buying by the bank to complete the buyback.

Buying back stock does not guarantee that prices will start to recover. For example, Imperial Bank shares have fallen 10 percent since its buyback program was announced.

Nonetheless, an increasing number of companies are giving such programs a try, even those that have not been public for very long.

PBOC Holdings Inc., the parent of People’s Bank of California, held its initial public offering in May. Since then, the share price has drifted lower, bottoming out at $8.50 at the start of this month.

In response, the company announced on Sept. 2 that its board had approved the repurchase of up to 1 million shares, or around 5 percent of its outstanding stock.

“Small caps and financial stocks have all fallen a lot since our IPO,” said Michael Holmes, PBOC’s chief financial officer. “Out stock fell to a price that we felt was attractive. And given that we are optimistic about the future of this company, we decided to buy.”

Brokers pointed out that while buybacks are usually a positive event, they do not always mean a company’s management expects the firm’s stock price to rebound any time soon.

“It is always good to see it, but you have to make sure it is for the right reasons,” said Riley. “A lot of management has a lot of stock. And they get sick of seeing the share price falling, so they may just want to support the stock.”

A more positive sign is if high-level executives are using their own money, rather than the company’s, to buy up shares, he said.

He pointed to L.A.-based real estate marketing and property management company Kennedy-Wilson Inc., whose management team in recent weeks has bought around 6 percent of the company’s outstanding shares with its own money.