A retirement pension plan that allows an employee to make annual contributions to the plan, based on a percentage of compensation, with some of it usually (but not always) matched by the plan sponsor. Contributions and earnings thereon are tax-deferred. There is no guarantee as to the eventual level of benefits to be provided by this plan. The participant selects the desired investment options, which may be changed at regular intervals. The plan sponsor periodically reports to the participant on the amount that is in his or her account. The level of benefits ultimately payable out of plan assets is variable, and depends on the investment performance of the participant's selected asset mix.