In 1980, more than 60% of American workers who had retirement plans at work enjoyed traditional pensions, with the employer providing fixed monthly payments throughout the former employee’s retirement. Most other employees had “defined contribution” plans such as 401(k)s, which leave retirement investing to the employee. Today, the numbers are reversed, with more and more companies scrapping traditional pensions and shifting the investing risk to their workers. But numerous studies have found that the typical worker saves too little, often invests too conservatively and doesn’t manage the nest egg well after retiring. Millions could end up with too little to live on as they grow old. If 401(k)s and similar plans are the main way Americans invest for retirement, how can employers improve them?…