The stock market is up modestly through the first six months of the year, amid increasing volatility and concern.

The 1 to 3 percent rise in the Piper Jaffray-Star Tribune Minnesota index, the S&P 500 and Russell 3000 index of public companies has slipped since January highs. And the indexes haven’t kept pace with projected increased earnings of American companies this year.

“We’re still expecting a flat market for the year,” said CEO Mark Henneman of St. Paul investment firm Mairs and Power. “We expect the S&P 500 earnings to rise nearly 20 percent this year. A lot of that is from [last fall’s tax cut], which was expected and caused the market to be strong last year.

“The market is also getting concerned the economy is overheating. And the yield curve [a key indicator that involves the spread between short-term and long interest rates] has flattened considerably. That could be pointing toward slower growth in the future.”

The stock market is heading toward an unprecedented postwar 10-year bull market that has seen the S&P 500 rebound from a Great Recession low of about 780 to a high of 2,873 in January. It was trading around 2,725 last week.

Skeptics have said for weeks that we may be in for a slight recession later this year or next, often preceded by a market correction of up to 10 percent.

“There’s a struggle between bulls and bears,” Jim Paulsen, chief investment strategist at the Leuthold Group, told investors last week. “Are we on the final legs of this bull market? I’m impressed with how narrow is the path for the bulls.”

Paulsen was right in 2009-2010 when he predicted a long, slow economic recovery, aided by accommodative Federal Reserve monetary policy that kept interest rates low. He is less sanguine now.

The recovery finally hit Main Street in force by 2012-2013.

Economic growth has averaged about 3 percent. Wages are increasing at close to 3 percent. And unemployment in the nation, at under 4 percent, is the lowest in 20 years. (It’s closer to 3 percent in the Twin Cities area.)

And interest rates are rising, another factor that tends to work against stocks rising.

President Donald Trump remains the wild card.

He railed against Wisconsin-based Harley Davidson last week, after it said it was moving some production to its facilities in Brazil, India and Australia to serve a growth market. That was in response to Trump’s threatened tariffs and trade war, which critics said will hurt U.S. growth and workers.

Similarly, Twin Cities-based Polaris, whose stock price is down about 11 percent over three years, said it may move some of its motorcycle production overseas because of tariffs. Polaris also has been dogged by significant and expensive product-safety issues.

Other critics have said Trump understands the economy as a 1970s entity. They lament that his tariffs on imported steel and aluminum will actually hurt U.S. companies, because most of them don’t produce bulk steel.

They add value by extruding aluminum and steel into higher-value frames, parts and products for many industries and consumer goods. Just Friday, General Motors warned that expansive tariffs could raise the cost of vehicles, reduce sales and cost jobs.

Earlier, auto-trade groups warned that imposing tariffs on imported vehicles could threaten hundreds of thousands of auto jobs.

Paulsen said his worst concern is that interest rates keep rising while economic growth slows to 2.5 percent or less in the back half of 2018.

“It’s very hard to see what’s going to goose the economy further [beyond the $1.5 trillion in tax cuts that benefited disproportionately corporations and affluent Americans],” Sonja Gibbs, senior director of capital markets at the Institute of International Finance, told the New York Times last week.

“That’s why everyone is bemoaning the flattening of the yield curve.”

To be sure, the market is near record highs, more Americans are working than ever and the economy is growing.

However, Trump and Congress also have reversed several years of declining federal deficits under President Barack Obama. The ballooning national debt also can “crowd out” private investment and help slow the economy.

The best-performing Minnesota companies so far this year, and the last three, include smaller, narrowly focused medical manufacturers.

That includes Intricon, the 40-year-old microelectronic manufacturer that seems to be disrupting the once-staid and pricey hearing aid industry with a lower-cost product that works for up to 80 percent of hearing-loss patients.

Surmodics, which provides coatings for implantable medical devices and also performs diagnostics, is enjoying its best performance in a decade.

And Tactile Systems of Minneapolis which went public last year at $10 per share, has traded over $50 per share recently. The U.S. Food and Drug Administration has cleared Tactile to use its Flexitouch at-home treatment for lymphedema swelling in the head and neck, as well as for swollen limbs, treating the excess fluid buildup that often results from cancer treatment. Flexitouch has been recognized as an economical way to treat lymphedema with a system that costs about $5,000 instead of repeated clinic visits and open-ended hospital stays.

Martha Pomerantz, the veteran portfolio manager and Minneapolis partner in Evercore Wealth Management, isn’t too concerned about the market, considering the nearly 250 percent increase since the depths of 2009.

“The market’s volatility year-to-date is tied to concern about the impact of possible trade restrictions and eventual increases in interest rates,” Pomerantz said in an e-mail. “So much of that is sheer speculation. It is easy to let emotions overtake rational thought.

“Good long-term investing requires staying focused and tuning out the market noise. U.S. corporate earnings are strong. We think it is more likely than not that inflation will stay in check given changes in demographics, technology and globalization.

“Valuation for the U.S. market as a whole is more attractive today particularly in light of the pickup in earnings growth. U.S. investments are likely to fare better than those overseas given trade is a fairly small portion of our economy. For longer term investors, this volatility can present buying opportunities.”