Going public was once a sign of a young startup's promise. But these days, a growing number of young companies are avoiding IPOs altogether. In 1997, the average age of US-listed firms was a sprightly 12 years old. Now the average age is 20. US public companies have also gotten bigger. Between 1975 and 1991, around...

Going public was once a sign of a young startup's promise. But these days, a growing number of young companies are avoiding IPOs altogether. In 1997, the average age of US-listed firms was a sprightly 12 years old. Now the average age is 20. US public companies have also gotten bigger. Between 1975 and 1991, around...