It doesn’t matter if a company makes beds, barbecue chicken or iPhones. These days, it seems no business is off limits to “activist” investment firms that buy up shares and demand change.

Calls to revamp boards of directors, install a new CEO or cut executive pay are higher than ever in 2015 with no signs of letting up. Increasingly, inflammatory letters that call for a different corporate strategy or faster results are becoming mainstream investment tactics.

Activists have challenged management at blue-chip companies such as Apple, General Motors and DuPont, while Minnesota companies that have drawn activist attention dot the Star Tribune 100 list of the state’s biggest companies. Last year they included Famous Dave’s, ValueVision and Target. Next week, activist initiatives at Select Comfort and Imation will come to a head.

“In every aspect, [activism] is on the rise,” said Matt Arnold, an equity analyst at Edward Jones.

Last year, 33 proposals from activist firms went to shareholder votes. So far in 2015, the shareholder advisory firm Institutional Shareholder Services (ISS) has tracked 35.

The activists are becoming bolder, too. Traditionally, “the sweet spot for activists” has been the medium-sized public company. But some investor groups now seek larger targets, said Subodh Mishra, an ISS spokesman.

In 2009, the median stock market valuation of corporate targets was $94 million, ISS found. By mid-2014, it was $255 million. Battles in play now involve companies with average market values of $623 million.

A tale of two proxy fights

Next week, shareholders of Oakdale data-storage firm Imation — with a market cap of $175.3 million — and of Plymouth-based bedmaker Select Comfort — with a market cap of $1.61 billion — will vote on investor proposals to replace board members at their annual meetings.

The boards of both companies urged shareholders to vote no.

At Select Comfort, Blue Clay Capital — which owns 2 percent of the stock — wants to pick two board members and to curb Select’s spending after a long run of new stores, ads, remodels and computer systems.

Blue Clay has had some recent success. Last year, it won a proxy battle with Famous Dave’s that resulted in CEO Ed Rensi’s appointment.

Select Comfort declined an interview request, but recently wrote regulators and shareholders saying Blue Clay’s ideas were “risky” and “poorly conceived.” The company also noted its profit improvements.

In contrast, Imation is struggling. The company last Wednesday posted another quarterly loss, this time for $14 million.

New York-based Clinton Group wants Imation shareholders to vote for its three board nominees and its proposal to slash board and executive pay.

The group wrote shareholders and regulators alleging years of losses and mismanagement. It also noted a sinking stock price that now sits near $3.90 a share.

“The board’s views on compensation … would suggest that they believe they are doing a great job, which we believe is diametrically opposed to any data we have examined,” wrote Joseph De Perio, a senior portfolio manager for Clinton.

Imation CEO Mark Lucas said earlier this year that he was frustrated that attempts to negotiate with the Clinton Group proved unsuccessful. Lucas also said that Clinton officials declined to say what they wanted Imation’s management to do differently.

More shares, bigger stakes

Activists have been around for decades — think billionaire corporate raider Carl Icahn, who bought up and sold off Trans World Airlines in 1985 and who made bold runs at Apple and Family Dollar last year.

But their willingness to buy up large shares of a company’s stock has never been greater.

JP Morgan recently tracked investments by activist hedge funds and found that they managed less than $12 billion in 2003.

At the beginning of this year, they managed more than $112 billion. Most of that growth has taken place since 2009.

On average, JP Morgan said, companies facing activist motions had underperformed the market by 10 percent.

“These [activists] are looking everywhere for performance anomalies,” said Alfred Marcus, strategic management professor at the University of Minnesota’s Carlson School of Management.

“It’s any company performance that is not in line with expectation that attracts these private equity people, because they think they can turn it around.”

Often, investors first try to talk to companies quietly, without waging a public battle, said Arnold at Edward Jones.

Sometimes proxy fights prove a waste of money. In other cases, the outsider pressure nets good results, Arnold said. Often calls for change “will help all investors regardless of the proxy vote outcome, because it creates a heightened sense of urgency to deliver results.”

Returns aren’t always better

Sometimes the funds demanding change don’t get the returns they wanted. About 30 percent of activist hedge funds tracked by JP Morgan underperformed from 2009 to 2014.

Separately, average shareholders don’t always get to decide a proxy outcome.

Deals are often made to avoid a contentious annual meeting that address the weakness pointed out by the activist.

Recently, General Motors investor Harry Wilson demanded the automaker repurchase more shares of stock.

GM struck a deal with Wilson instead of taking it to the annual meeting.

It will now buy back $5 billion in stock and spend some socked-away cash on growth. In exchange, Wilson dropped his demand for a seat on the board.

Other disputes go to a full vote. Nelson Peltz’s investment group wants DuPont to split into two firms — putting growth areas in one company, and cyclical units into another. His hedge fund is going after four seats at DuPont’s annual meeting Wednesday.