Minneapolis-based Clifton Group has agreed to be purchased by a subsidiary of investment heavyweight Eaton Vance.

Seattle-based Parametric Portfolio Associates said Monday that it plans to buy Clifton Group Investment Management for an undisclosed price.

Clifton manages $33 billion for about 180 institutional clients. The firm specializes in custom risk management and futures- and options-based strategies.

Clifton is 80 percent-owned by Minneapolis-based Dougherty Financial Group and 20 percent owned by its three principals: Jack Hansen, chief investment officer; Thomas Lee, senior portfolio manager, and Kip Chaffee, managing principal.

The three owner-executives will continue in their current roles at Parametric under long-term employment contracts.

Clifton will operate as a division of Parametric, with Chaffee reporting to Brian Langstraat, Parametric's CEO. Parametric manages $53 billion for institutions, high-net-worth individuals and fund investors.

Boston-based Eaton Vance and its affiliates manage almost $200 billion in assets. The Clifton deal is expected to be completed by year's end.