South Koreans in Seoul watching a speech by Kim Jong-un, the North Korean leader. “Above all, we must ease the acute military tensions between the North and the South,” he said.

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Good morning.

Here’s what you need to know:

• South Korea has proposed high-level talks with North Korea next week, after the North’s leader, Kim Jong-un, called for negotiations to ease military tensions and to discuss his country’s participation in the Winter Olympics, which will be hosted by the South next month.

In his New Year’s Day speech, Mr. Kim said the North was capable of striking the mainland U.S. with a nuclear missile. “I have a nuclear button on the desk in my office,” he said.

In an analysis, our correspondents say the comments represent “a canny new strategy to initiate direct talks with South Korea in the hope of driving a wedge into its seven-decade alliance with the United States.”

The largest demonstrations in the country since 2009 entered a sixth day today, with at least 21 killed and 450 arrested.

The protesters are voicing discontent with the pace of political and economic change, even though many sanctions against Iran have been lifted. The weak economy particularly affects the young. Officially, youth unemployment is near 20 percent, but experts say it’s closer to 40 percent.

Iran’s supreme leader, Ayatollah Ali Khamenei, blamed the country’s “enemies” today for the protests, his first comments since the unrest started.

An image taken from video showed the aftermath of protests in Tuyserkan, Iran.

A wave of optimism in American businesses is bringing investment in new plants, equipment and factory upgrades that could create jobs — and perhaps raise wages.

Initially inspired by the Trump administration’s regulatory pullback, executives are also encouraged by continued economic growth.

“The notion that deregulation unleashes growth is virtually impossible to find in the data,” said a onetime economic adviser to former Vice President Joe Biden. “What does matter is this idea that confidence matters. If their expectations about the future are positive, then it does make a difference.”

• Millions of people in the U.S. have fallen victim to painkiller abuse, alcoholism, the rise of meth and the revival of heroin. As a result, entrepreneurs are sweeping in.

Our multipart series examines the industry of addiction treatment, which is haphazardly regulated, poorly understood and expanding at a rapid clip.

In the first installment, we look at one of the biggest addiction-treatment companies in the country, and how the death of a patient nearly brought it down.

• Addressing readers of The Times, A. G. Sulzberger explains his approach to the job in a period when “misinformation is rising and trust in the media is declining.” Read his comments here.

He’ll also be answering readers’ questions. Submit yours.

Rupert Murdoch’s decision to sell most of 21st Century Fox to Disney has many wondering what the future holds for him and two sons.

Our DealBook columnist, Andrew Ross Sorkin, looks at the biggest deals of 2017, and the year’s big winners.

Fungi could play a role in improving laundry detergents and, by extension, in reducing…