NEW YORK ( TheStreet) -- For years, institutional investors followed standard strategies. Institutions maintained static portfolios, keeping 60% of assets in stocks and most of the rest in fixed income. The approach worked beautifully in the 1990s, but it has produced skimpy results in the past decade.Now more advisers are challenging the traditional thinking. Among the more interesting dissenters is Tim Knepp, chief investment officer of Genworth Financial Advisors, who oversees $7 billion in assets. Knepp says standard strategies failed to protect investors during the stock-market meltdown. To support his view, he cites data on performance of portfolios during the 10 years ending in 2009. During that period, a portfolio that was 60% in the S&P 500 Index and 40% in the Barclays Aggregate Bond Index would have returned a meager 2.3% annually. In the downturn of 2008, the diversified portfolio would have lost 22%. The results would have also been poor in portfolios that included a variety of assets, such as small-cap stocks, commodities and foreign bonds. Seeing such data, proponents of conventional diversification remain unmoved. They say that by holding a standard 60-40 portfolio long enough, investors will obtain decent results. Knepp counters that investors who stick with static allocations are bound to suffer big losses periodically. He says investors should make tactical moves, shifting allocations as different assets become riskier. "There are some years when an investor who can stand moderate risk should have 60% in equities, and other years when it would be appropriate to have 70% of assets in bonds," he says. Genworth offers a series of portfolios designed for investors with different risk tolerances. The portfolios, sold by financial advisers, invest in mutual funds as well as individual securities. The most aggressive portfolio is for investors who can stand to lose 20% of their assets in one year. When risks became greater toward the end of 2008, the aggressive portfolio had 35% of assets in equities. Now that markets have stabilized, the equity allocation has been raised to 70%. Proponents of standard diversification suggest holding broad collections of stocks that track benchmarks, such as the S&P 500. But Knepp often emphasizes narrow sectors. Lately he has been targeting mutual funds that can prove resilient during market downturns.