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You may be counting on Social Security, but if you're not counting Social Security as a part of your overall asset allocation, you may be missing out on bigger gains in your retirement-savings portfolio.

Some financial advisers say retirement investors should consider the value of their Social Security benefits as a piece of their fixed-income investments.

Generally, adopting that strategy would mean shifting a big portion of your investible assets out of bonds and into stocks.

For example, if you've got $300,000 worth of Social Security benefits and a $700,000 investment portfolio, then your total portfolio is worth $1 million. If you wanted 50% of that portfolio, or $500,000, allocated to fixed-income investments, then just $200,000 of your investment portfolio would be in bonds, while $500,000 would be in equities.

There are different ways to gauge the present value of future benefits; one simple tactic is to add up your monthly benefit (you'll have to guess how long you'll be alive to collect benefits).

"We go through a process where we value someone's Social Security like a TIP," or Treasury Inflation Protected security, said Bill Meyer, chief executive of Social Security Solutions, which offers fee-based claiming tools and services. "Then we add it into the household's allocation."

In one scenario involving a hypothetical single person who claimed benefits at age 70, owned an investment portfolio worth $500,000, and employed a tax-efficient withdrawal strategy, Meyer said he found that this strategy led to 8 extra years of retirement income, compared with not counting Social Security in the person's investment allocation.

Famed investor Jack Bogle, founder of the Vanguard Group, seems to agree. In an interview in June with investment researcher Morningstar, Bogle suggested retirement savers should consider the value of their Social Security benefits in their asset allocation.

First Bogle cited his penchant for basing one's asset allocation on one's age. (If you're 40 years old, you have 40% of your investments in fixed income and 60% in equities. By the time you're 60, you've got 60% in fixed income, 40% in equities).

Then he talked about Social Security, citing a saver who has $300,000 saved in an investment portfolio.

"If you capitalize that stream of future payments, most people's Social Security is going to be…let's say $300,000 for an average investor," Bogle said. "If you have $300,000 all in equity funds, even equity-index funds, and $300,000 in Social Security, you are already at 50/50" fixed income versus equities, he said.

Meyer, of Social Security Solutions, acknowledged that many people "will be uncomfortable with taking on a larger stock position," he said.

In his practice, after coming up with a value for a client's Social Security benefits, the next step is a conversation with the client.

"That's where Social Security meets risk management," he said. "What does this really mean to have more stocks? How are you going to feel when the market goes up and down? A lot of people will say, 'I understand this concept but I really don't feel good when my 401k goes down $50,000,'" Meyer said.

People need to understand that "with the additional stock exposure there will be more volatility," Meyer said. "With our clients, we'll give them a target asset allocation and then we'll give them a range."

He tells clients: "Given your amount of Social Security, you could tilt your equity exposure as much as X."

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Then, Meyer said, "We show them the additional money they can get by having more stock. But then we run a Monte Carlo simulation to show them the volatility. What's the most you could win, but what's the most you could lose."

Also, he warned, married couples -- who can employ a variety of Social Security claiming strategies -- might have a harder time estimating the value of their future benefits.