Companies looking to increase participation may want to consider an Auto-Enrollment plan. New employees are automatically enrolled when they come on board, at 3%. That amount climbs to 6% by year 5. Employees can opt out at any time, and the plan can be set up that any funds they put in can be returned within the first 90 days.
Investments get contributed into one of several QDIA (Qualified Default Investment Alternative) plans, typically a balanced fund or a target-date fund.
In addition, if you are a safe-harbor match company, that option still remains, although the numbers change a little. Under a QACA (Qualified Automatic Contribution arrangement), the employer matchs the first 1% of salary contributed by the employee at 100%, and then 50% of the next 5%, for a total of 3.5% possible matching contributions. If you do this, you are exempt from the various discrimination testing requirements.
While its not for everyone, Automatic Enrollment typically sees 90% or better participation, and can be a big imporvement to your plan!