When mutual fund company American Century recently announced the rollout of a new line of target-dated Collective Investment Trusts (CITs), it was the latest evidence that plan sponsors are demanding alternative structures to the defined benefit and defined contribution plans they offer their employees.

"We initially offered CITs in the early 2000s but there wasn't enough traction to keep the funds going," explains Drew Billingsley, vice president of Institutional Product Strategy at the Kansas City-based investment company. "In 2009 we launched a new line-up of CITs. At that point we were trying to get out ahead of what we saw was an emerging trend. With this latest rollout of target-date funds, we were responding to direct demand, specifically from Lockton, who in this case is the sponsor, as we manage money for Lockton plans."

Take an anecdotal survey of advisors hoping to expand their reach into the 401(k) market and you're likely to find a good number of investment professionals who aren't well acquainted with CITs. But that is changing, and quickly. American Century's line of CITs has grown to about $1.5 billion in assets since 2009.