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]
The doctor or lawyer, for instance, could use her or his income to invest in a medical start-up or buy shares of medical companies he understands such as Johnson & Johnson. Over time, the nature of compounding, dollar cost averaging, and reinvesting dividends can result in her or his portfolio generating substantial passive income. The downside is that it can take decades to achieve enough to truly improve your standard of living. However, it is still the surest path to wealth based on the historical performance of business ownership and stocks.
As interest rates have been going down over the past 30 years, bond prices have continued to go up. With the 10-year yield (risk free rate) at roughly 2.55%, and the Fed Funds rate at 1.5% (two more 0.25% hikes are expected in 2018), it’s hard to see interest rates declining much further. That said, long term interest rates can stay low for a long time. Just look at Japanese interest rates, which are negative (inflation is higher than nominal interest rate).

The thing is, I’m not talking about buying brick-and-mortar buildings. I tried that many years ago with my father-in-law, and with devastating results. We tried to buy a duplex once, and the deal fell apart after we realized we weren’t really prepared for the purchase. I secretly wanted to become a landlord, but at the same time, I knew it wasn’t for me.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.