For example, writing a book is a passive income stream. You write it once and sell it over and over. The word passive is a little deceptive because you need to market the book. Nevertheless, compared to non-passive sources of income, which you need to do over and over to make money, such as providing a service, passive income streams require less time once they’re created. Other forms of passive income include other written works (i.e., courses), audio or video creations, affiliate marketing, licensing your idea, franchising, or continuity programs (i.e., memberships).
Since 1965, the use of high-yielding varieties of seeds, increased fertilisers and improved irrigation facilities collectively contributed to the Green Revolution in India, which improved the condition of agriculture by increasing crop productivity, improving crop patterns and strengthening forward and backward linkages between agriculture and industry.[129] However, it has also been criticised as an unsustainable effort, resulting in the growth of capitalistic farming, ignoring institutional reforms and widening income disparities.[130]
An obvious example is over exposure to bank stocks, which have been excellent investments for over a century.  Though a foundation of most portfolios, bank stocks do involve more risk at certain stages of the economic cycle than many realise.  Being less exposed to bank shares in the last few months could have preserved some capital.  So, a more diversified approach can help mitigate some of these risks.