By 2030, around 20 percent of the U.S. population will be 65 and older, up from 13 percent today, reckons the Census Bureau. There's a gloomy theory on how that will affect stocks. As boomers earned and saved in the 1980s and 1990s, the market soared, the thinking goes. As they retire and draw down their savings, share prices could deflate.

Nonsense, concluded the Government Accountability Office in a 2006 study. Baby boomers own less than a quarter of the U.S. stocks and bonds held by U.S. savers, so their influence on prices is overstated, according to the authors. Anyhow, many old folks spend down their assets slowly and continue to save.

But if there's one thing economists can be counted on for it's to publish perfectly contradictory, equally convincing findings. Researchers for the Federal Reserve Bank of San Francisco recently wrote that the historical link between age distribution and stock returns suggests the boomer retirement "could be a factor holding down equity valuations over the next two decades."

These two divergent views would seem to prescribe radically different investment approaches, with a steep penalty for guessing wrong. But maybe not. What boomers will really want in retirement is more investment income, says Savita Subramanian, a strategist for Bank of America Merrill Lynch. "If you think about it, yield is scarce at the moment, and competition for it is only going to increase."

To her first point, on average over the past 50 years, investors who spent $1 million on 10-year Treasury bonds could have looked forward to a yearly income of $67,000. At recent rates, the same investment would provide just $21,000. And the percentage of dividend-paying firms in the S&P 500 index fell to 75 percent in 2010, from 94 percent in 1980.

The dividend decline is beginning to reverse, however. The percentage of payers hit 78 percent in 2011. Still, some companies can afford to pay much more: S&P 500 companies distribute barely one-third of their operating profits as dividends their stingiest amount ever. Nonfinancial companies in the index hold more than $1 trillion in cash.

Companies in the best position to supply boomers with steadily rising dividends in coming decades will be rewarded with plenty of demand for their shares, says Subramanian. She recommends a could-would-should strategy for investors looking for such firms. Companies that could raise payments include those with plenty of cash and modest debt. Firms that should are those with high returns on equity and stable earnings despite slow growth. And companies that would are those that most likely already are. A recent screen for all these attributes produced the firms below.

• Baxter (BAX)
• Coca-Cola (KO)
• Deere (DE)
• 3M (MMM)