Retirement account owners make similar asset allocations in stocks and interest-earning assets whether investing in IRAs or 401(k)-type plans, a new study finds.

The study by the Employee Benefits Research Institute, Washington, did find some differences among the 2 kinds of accounts, however, depending on such factors as income and educational levels of the plan owners.

Overall, 29% of owners of IRAs invested entirely in stock-based investments, while 23.9% invested in all interest-earning assets, EBRI found. The remaining 47.1% mixed their investments.

Among 401(k) plan participants, 29.1% invested in all stocks, while 21.3% invested in all interest-earning assets and 49.6% invested in mixed assets.

Both IRAs and 401(k)-type plan owners were more likely to invest in stocks as their educational levels increased, EBRI found.

Similarly, as family income went up, the percentage of participants with all assets invested in interest-earning assets went down.

In addition, both those who own 401(k)-type plans and those who own IRAs are more likely to be invested all in stocks if they also own the other type of plan, EBRI found.