Instructions: This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Input: Passage: Income inequality has become a hotly debated topic globally. According to the CIA World Factbook, U.S. income inequality ranked 41st highest among 156 countries in 2017 (i.e., 74% of countries have a more equal income distribution). According to the Congressional Budget Office, the top 1% of income households earned about a 9% share of the pre-tax income in 1979, versus 19% in 2007 and 17% in 2014. For after-tax income, these figures were 7%, 17%, and 13%, respectively. These figures indicate the share of income earned by top earners more than doubled between 1979 and 2007, then fell somewhat following the Great Recession, and the higher tax rates and re-distributive policies applied by President Barack Obama in 2013 (i.e., expiration of the Bush Tax Cuts for the top 1% and subsidies for lower income persons via the Affordable Care Act). Recasting the 2012 income using the 1979 income distribution (representing the more egalitarian 1950-1980 period), the bottom 99% of families would have averaged about $7,100 more income. Income inequality in the United States has grown from 2005 to 2012 in more than 2 out of 3 metropolitan areas.
Question: How many years was the egalitarian period 1950-1980?
Answer type: Number
Output:
30.