What evidence is there that mao´s great leap forward was a failure?

There's lots of evidence that show that the ''Great leap forward'' was a big failure. The most evident ones were the increased poverty of the Chinese population, the bad economic planning that was making enormous troubles to China just to survive, the very common starvation because of lack of food because of bad planning, closing the country's market for trade.

the statment would be a easy nonviolent one

norsemen from northern countries had made earlier journeys