Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Let me give you an example: Passage: Martin Luther married Katharina von Bora, one of 12 nuns he had helped escape from the Nimbschen Cistercian convent in April 1523, when he arranged for them to be smuggled out in herring barrels. Suddenly, and while I was occupied with far different thoughts, he wrote to Wenceslaus Link, “the Lord has plunged me into marriage. At the time of their marriage, Katharina was 26 years old and Luther was 41 years old. Question: In a letter who did Luther credit for his union with Katharina?
The answer to this example can be: the Lord
Here is why: The paragraph clearly states that, Luther has credited the Lord for his union with Katharina, hence the Lord is correct answer.

OK. solve this:
Passage: Economist Joseph Stiglitz presented evidence in 2009 that both global inequality and inequality within countries prevent growth by limiting aggregate demand. Economist Branko Milanovic, wrote in 2001 that, 'The view that income inequality harms growth – or that improved equality can help sustain growth – has become more widely held in recent years. ... The main reason for this shift is the increasing importance of human capital in development. When physical capital mattered most, savings and investments were key. Then it was important to have a large contingent of rich people who could save a greater proportion of their income than the poor and invest it in physical capital. But now that human capital is scarcer than machines, widespread education has become the secret to growth.' Question: What has been the main reason for the shift to the view that income inequality harms growth?
Answer:
increasing importance of human capital in development