Manager tenure is one of many important criteria to consider in the search for a worthy mutual fund. Although past performance is never a guarantee of future results, a long-tenured manager with a record of success through varied market environments is generally more likely to produce continued success than a manager with little experience at the helm. Here are several successful mutual fund managers in the global equity space, each with at least 15 years of tenure on a single fund.

Frank V. Jennings

Frank V. Jennings joined OppenheimerFunds, a subsidiary of Massachusetts Mutual Life Insurance Company (MassMutual), in 1995. He immediately took the reins of the Oppenheimer Global Opportunities Fund ("OPGIX"), which focuses on opportunistic equity investments identified through fundamental research and analysis. As of April 27, 2016, Jennings led the fund to a four-star overall rating from Morningstar in the world stock category, including a three-star 10-year rating. It has a five-star rating for the most recent three-year period. OPGIX produced the second-highest average annual total returns in the category during the last 15 years at 8.53%. The fund has $3.6 billion in assets under management (AUM).

Jennings earned a bachelor's degree in economics at Emory University in Atlanta before going on to complete a doctorate in economics at the University of Geneva in Switzerland. Prior to joining OppenheimerFunds, Jennings served as managing director of global equities at Paine Webber and Company, which has since merged into UBS Group AG (NYSE: UBS).

David R. Mannheim

David R. Mannheim joined MFS Investment Management, a subsidiary of Sun Life Financial Inc. (NYSE: SLF), in 1988. He worked as an equity research analyst until 1992, when he was named portfolio manager of the MFS Global Equity Fund ("MWEFX"). MWEFX focuses primarily on reasonably priced large-cap stocks with growth characteristics. As of April 27, 2016, Mannheim led the fund to a gold analyst rating from Morningstar, in addition to a four-star overall rating and a five-star 10-year rating in the world stock category. The fund has a three-star rating for the most recent three-year period. MWEFX produced annual average total returns of 7.19% during the last 15 years. It has $2.4 billion in AUM.

Mannheim completed his undergraduate education at Amherst College in Massachusetts and went on to complete a master's degree at the MIT Sloan School of Management. Mannheim worked briefly as a bank loan officer before joining MFS. He has served as director of international equity portfolio management at the firm since 1999. He is also a member of the firm's global equity management committee.

Robert W. Lovelace

Robert W. Lovelace joined Capital Group in 1985 as a mining and metals industry analyst. In 1994, he began working as a portfolio manager on two mutual funds under the Capital Group's American Funds label. In 2000, he took the reins of the long-lived American Funds New Perspective Fund ("ANWPX"). The fund focuses primarily on blue-chip multinational companies with growth characteristics linked to changes in global patterns of trade and other economic and political influences. Lovelace has a 15-year tenure with the fund and leads a management team with an average tenure of 10 years. As of April 27, 2016, ANWPX had a gold analyst rating from Morningstar and a five-star overall rating in the world stock category. It also has a five-star rating for the most recent 10-year period and a four-star rating for the most recent three years. The fund produced a 15-year annual average total return of 7.02%. It has $61.1 billion in AUM.

Lovelace earned a bachelor's degree in mineral economics from Princeton University. He also holds a chartered financial analyst (CFA) certification. Lovelace serves as president of Capital Research and Management Company, a Capital Group subsidiary. He is also a member of the Capital Group companies management committee, a team of seven people who oversee the Capital Group's global operations.

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