Insurance agent Antonio Galis discusses plans available in the third year of the Affordable Care Act, on Nov. 2 in Miami. (Joe Raedle/Getty Images)
Opinion writer

As the Black Friday stampedes will soon attest, Americans are among the most enthusiastic and aggressive shoppers in the world.

Yet when it comes to two of the most financially significant decisions in our lives — our health insurance and our jobs — we’ve proved exceptionally lazy. The latest data suggest that Americans are leaving billions of dollars on the table due to our reluctance to shop around.

It’s currently “open enrollment” season, the one time of year when most Americans are allowed to change their health insurance. Yet relatively few choose to do so.

It’s little wonder why. Insurance plans are complicated, with more moving parts and narrower doctor networks than in the past. Insurers don’t exactly go out of their way to make price comparisons easy, either. Plus, consumers have to go through the rigmarole of figuring out whether their preferred doctors participate in competing plans (though of course these preferred doctors could always drop out of their current plans, too).

All this results in relatively few people taking the time to learn about their alternatives. They just auto-renew whatever they have. If it ain’t broke, right?

This is exactly the attitude that insurers count on.

Multiple economic studies have found that insurers jack up rates on those too lazy or inattentive to investigate other options. Plans end up raising premiums, deductibles or co-pays from year to year, harvesting as much additional money from enrollees’ inertia as possible. Insurers take advantage of consumers’ vague recollection that they did their homework last year, or perhaps the year before, so they don’t need to repeat the exercise. But the plan that was the best deal a year ago could well be the worst one now.

Those with employer-sponsored health insurance theoretically should be shielded from some of this “harvesting,” since employers are supposed to negotiate on behalf of their workers. Consumers getting insurance through Medicare Advantage, Medicare Part D and the Obamacare exchanges are at greater risk.

A recent report from the Department of Health and Human Services found that only about a quarter of people who enrolled in plans on the Obamacare exchanges in 2014 switched plans in 2015. Those who did, and who moved to a plan with about the same level of coverage (from one “silver plan” to another, for example), saved on average nearly $400 annually on premiums relative to what they would have paid had they remained in the same plan.

This year, if all Obamacare consumers switched from their current plan to the lowest-premium plan in the same “metal level,” they would save an average of $610 annually before tax credits. Total savings to consumers and taxpayers (counting both premiums and tax credits) would be more than $4 billion.

Over time, the savings would likely grow even larger, because more attentive consumers would force insurers to price more competitively in the first place. That in turn might bring down the prices that doctors and hospitals charge, too.

“The less attentive are consumers, the easier it is for premiums to go up, and therefore the less pressure insurance companies put on hospitals to keep prices down,” said Kate Ho, a Columbia University economics professor.

Health insurance isn’t the only realm in which Americans’ fabled shopping prowess is coming up short. The other is their employment.

Despite anecdotes about workers today (especially those good-fer-nothin’ millennials) having no sense of loyalty to their employers, job-hopping has slowed dramatically. The share of workers switching from one job to another in a given month has fallen by nearly half since the mid-1990s, according to Labor Department data.

This reluctance to job-hop is one reason wage growth has been so weak: The main avenue through which workers, and especially young workers, get raises is by changing employers. Millennials stand to gain the most by switching employers, since they entered the job market during a weak economy, when they had little choice but to accept bargain-basement wages.

True, it was hard to shop around for jobs a few years ago, back when no one was hiring. But today job openings are close to all-time highs, yet risk-averse workers still seem pretty reluctant to jump ship.

When it comes to friendships, spouses and sports teams, loyalty is a virtue. But when it comes to shopping for the best deals for your health care and your career, your loyalty can come at a huge cost.