If you're looking for a growth industry to invest in over the next couple decades, forget Web-browsing cell phones, GPS devices and other high-tech gadgetry. Instead, take a look at companies that make bifocals and hearing aids.

The Census Bureau underscored that point last week in releasing updated population projections that predict the 65-and-over age group will double by 2050. By 2030, it said, one in five Americans will be at least 65 years old.

Although the California population is younger than that of the nation as a whole, the Golden State will have its own gray wave. The California Budget Project this month, using state demographic data, projected that while the state's overall population will increase by 29.4 percent by 2020, the number of those 65 and older will soar at a rate nearly three times as fast — 75.4 percent.

In terms of what this will mean to society, the good news is that these will not be your grandparents' grandparents. The bureau reports that older people today have lower rates of disability and are less likely to live in poverty than previous generations. They can expect to live longer — but, alas, not forever.

So, while the implications of the coming surge of seniors on social service and healthcare systems are not as immediately severe as they might have been 25 years ago, it is inevitable that those systems will be challenged. There is no guarantee that a healthy, financially self-sufficient 70-year-old will not become an infirm 80-year-old reliant on government services for survival.

Retirement savings can wear down over time, as does the human body.

As it happens, all of this plays into the political theater that was played out in California's Capitol last week, during lawmakers' latest exercise in running-in-place on the state budget stalemate.

The issue of the moment was legislative Republicans' demand for a hard cap on state spending increases. They want to place a constitutional amendment on the ballot that would limit future spending increases to no more than the combined increase in inflation and population growth.

If tax revenue in a given year were to grow by more than that — which it generally does in decent economic times — half the surplus would be placed in a reserve account for a rainy day and the other half would be used to make accelerated debt repayments.

On Friday, the Democratic leadership of the Assembly granted a hearing on that proposal — a decision that kicked off a day of sound and fury at the Capitol.

Members of the Education Coalition staged a news conference to warn that such a spending cap would have unintended consequences. "It would lock us into a bad budget year as the new baseline funding year for schools," said Scott Plotkin, executive director of the California School Boards Association.

Whatever the impact on schools, such a spending cap would create a tension between spending on education and spending on everything else.

Under Proposition 98, the voter-approved school spending guarantee, education funding grows over time based on increases in per capita personal income and growth in student population. Since that growth is generally faster than inflation plus population increase, one likely effect of the proposed spending cap would be to squeeze all other state programs, including healthcare and social service programs for seniors.

"Any cap based on population will kill seniors over the next couple of decades," Gary Passmore, executive director of the Congress of California Seniors, told me. "Since the growth in the senior population will be triple that of the overall population, it will place incredible demands on things like nursing-home care and in-home support services."

Here's evidence of how a graying population might strain state healthcare services: The California Healthcare Foundation reports that while seniors now make up just 12 percent of Californians covered by Medi-Cal, they account for 28 percent of Medi-Cal expenditures.

Republican lawmakers say they welcome suggestions for other spending-cap formulas, but that Democrats have offered none. However, GOP lawmakers have also rejected as "phony" a spending cap proposed by Gov. Arnold Schwarzenegger.

The governor proposes that any revenue increases in excess of average annual revenue growth over the previous 10 years be placed in a rainy-day account.

That would have the effect of evening out the peaks and valleys in state revenue, but also allow state services to expand in times of sustained economic growth.

That would at least create the possibility that the state could keep pace with the needs of all those Californians who will be living longer than those who came before.

— Timm Herdt is chief of The Star state bureau. Read his political blog "95 percent accurate*" at http://www.TimmHerdt.com.