I read from a news article that North Korea is generally supported by a black market that the government generally accepts . What percent of the economy is supported by this black market and how much money does the North Korean government get from this black market?
I have no hard data, but to give you an idea of the legitimate market's comparative strength, prior to 2013, the Choco Pie snack cake (a brand of Moon Pies) had entered into the North Korean Black Market en mass due to it's use by South Korean employers at the Kaesong Industrial Region (KIR) to pay North Korean workers bonuses without using cash, which is illegal for North Koreans employed there to receive.
The result was that the confection became an almost de jure currency on the North Korean Black Market and was estimated to be worth just about $10 (USD) by South Korean News Paper The Chosun Ilbo and was rising and it was thought that the snack cake was edging out the North Korean currency (The Won) as the currency of choice for the black market and threatening to cause a currency crisis in the legitimate economy. When KIR reopened following the 2013 Korean Crises, limits were placed on the use of Moon Pies for bonuses with the state advising Noodles or Sausages as another product and NK has created their own brand of the Pie to stave off a speculation market bubble that had formed during the 5 month period where no new Choco Pies were entering the country through KIR bonus payments.
Suffice to say, North Korea's black market has a powerful economic share, given that it was able to introduce a de jure currency that nearly crippled the legitimate economy... and what's more, said currency was entirely backed by a snack cake. And as unbelievable as this may seem, here is the link to the Choco Pie Wikipedia Entry to confirm that this is indeed one of the most bizarre economic crises any nation has ever faced.
There's no firm data on this because NK is not publishing much if any info on its economy. But there are some expert estimates:
Not only does North Korea not publish economic data, but it has an important black market and rampant corruption. [...]
The typical North Korean household derives more than 70% of its income from market activities - both legal and illegal - according to Byung-Yeon Kim, economics professor at Seoul National University. He estimates more than half of market activities are illegal.
This makes measuring its economy particularly challenging.
"These market activities are quite prevalent and how to measure GDP in this kind of dual economy is a very big task," Byung-Yeon Kim said. "Even in well-developed capital economies such as Italy, it's very difficult to measure the informal economy."