In the 1960s, when venture capital was virtually unheard of, most investors were family offices and only tens of millions of dollars were invested in start-ups each year, recalled Franklin “Pitch” Johnson, who backed Amgen and Applied Biosystems. That grew to hundreds of millions of dollars in the 1970s, a few billion in the 1980s and $100 billion in the 1990s, when “we knew it wouldn’t go on,” he said.