PYONGYANG -- The streets of Pyongyang were busier than ever as roads that once were empty of cars flowed with traffic, CBS News correspondent Adriana Diaz reports. However, stop lights were rare, so patriotic traffic cops maintained order. A whole new neighborhood was being built, and the skyline was dotted with cranes.

North Korea’s economy shrank last year, but, Diaz says, the country looked like a place that was expanding, not one crippled by sanctions.

“The purpose of the sanctions is to squash us,” North Korean Ri Kum Jin told CBS News. “But we cannot surrender. We have to defend our lives and our nuclear program,” he said.

But it was precisely that nuclear program which prompted, in March, the United Nations to impose their harshest restrictions against North Korea in decades. The result was, in September, the fifth nuclear test carried out by the country so far.

“We have abundant natural resources that can be used for nuclear technology,” said economist Ri Ki Song, who advises on policy in North Korea. He was selected by the North Korean government for an interview with CBS News.

“It’s the nuclear threats made by the U.S. that caused all of this,” Song said. “The question is whether the new president is willing to abandon hostile policies. Your presidents all sanction us, and we just grow stronger.”

Despite this claim, Diaz reports, in 2016, the average person in North Korea earned just over a thousand dollars a year, less than half what individuals made in the 1980s. They were staying afloat because of China and its appetite for commodities like coal.

China bought 60 percent more coal from North Korea in August than in April, when the sanctions took effect. It did this by taking advantage of a humanitarian exemption in the law; a loophole which U.S. Secretary of State John Kerry wanted to see eliminated.

“It’s obviously being abused,” Kerry said. “Why is it being abused? The greatest amount of coal and the greatest amount of revenue historically has just passed between China and North Korea.”

China would have to sign on to any new U.N. sanctions against North Korea, and though they opposed the country’s nuclear program, they have so far been unwilling to go as far as Western powers wanted, Diaz reports. Their fear is that an economic collapse would send millions of refugees across their border, Diaz says, as well as American troops to their doorstep.