The quick interpretation of these figures is that, while employees in auto-enrollment plans may, in general, be better off, those who participate in plans without auto-enrollment may have a better savings strategy. In other words, although auto-enrollment brings more people into the plan, higher matching incentives lead to greater savings rates among participants in plans without auto-enrollment.

Which brings us to the bottom-line: It's the savings strategy that matters, not just the simple act of saving. Auto-enrollment succeeds because it removes decision paralysis from the equation. It does this by creating a new inertia. In auto-enrollment, no decision means doing the right thing (i.e., saving for retirement).

Here's the problem: This new inertia of default investing has a downside. Because it removes the need to make decisions, it also removes the necessary deliberation required when making decisions. Employees are too tempted to leave everything on autopilot. That's fine when you’re midflight and the course is already set; it becomes an issue when unanticipated winds cause you to veer off course — and let's not even talk about takeoff and landing.

Getting started in a 401(k) is not a strategic decision, but it is a critical first step. Auto-enrollment has proven to be an effective nudge for this. Beyond that first step, employees need a savings strategy, even when auto-escalation is used. That decision cannot be delegated or nudged.

Make sure your savings strategy isn't a turkey.