The most addictive games include four key elements: the illusion of progress, random rewards, a required timeliness and social sharing.

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The plan includes four key elements: stronger border security, creation of forgery-resistant proof-of-citizenship documents, fairer legal immigration for desirable candidates, and a "tough love" path to citizenship for those already in the United States.

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According to my ninth book, Capital Rising, co-authored with Srini Rangan, the EE consists of four key elements: transparent and efficient financial markets, reliable and effective corporate governance systems, human capital development systems, and clear and supportive intellectual property protection laws.

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