The overall benefits of such a program could reach 67 billion euros in operational efficiencies and energy savings if dynamic pricing becomes the default.

FORBES: Energy

If your employer signs you up to the Nest scheme (the government designed National Employment Savings Trust), then the default fund will be based on when you are expected to retire.

BBC: Investment choices after pension auto-enrolment

One reason for the growth: They are among the few permissible "default options" in many retirement plans, so investors may have their savings in target-date funds without actively choosing them.

WSJ: 'Target' Funds Still Missing the Mark on Returns