Yet a myopic Uncle Sam barely sees Renter-World.

Instead, Uncle Sam focuses on Owner-World. Owner-World captures the federal tax breaks: The homeownership tax deductions for mortgage interest and property taxes top $100 billion a year and are rising rapidly.

Owner-World also captures the federal attention: For almost 100 years, starting with a 1918 Department of Labor campaign and continuing through Franklin Delano Roosevelt's New Deal, Bill Clinton's National Homeownership Partnership, and George Bush's Ownership Society, the federal government has been promoting homeownership. Today 69 percent of households own a home -- an all-time high.

From Uncle Sam's vantage, that statistic marks success. Homeownership is the American "dream," the crucial first step on a family's pathway to the middle class. A homeowner amasses equity, so that one day he can own a piece of America. That vested interest spurs involvement in schools, in neighborhoods, in political life. Just as important, the home gives the owner a financial cushion. Even if owners do not reap the windfall of a superheated market, the home can still be a hedge against inflation.

Indeed, we are a nation of immigrants who have marked the exodus with a series of papers: green cards, citizenship, and mortgages. The ''American dream" may be a three-bedroom Cape on a tiny lot, but immigrants have come here for that dream.

So Uncle Sam's myopia is understandable. He expects renters to move on -- to become owners. That is what they too expect.

Renter-World, however, is in trouble.

Even though we are building new rental units, we are not adding to the net ''affordable" (a euphemism for cheap) units. That supply is shrinking. Between 1993 and 2003, we lost 2 million low-rent units from the rental inventory. At the same time, rents are rising, especially for newly constructed units.

Consider the plight of the lowest-income renters: 70 percent pay more than half their income for housing. The National Low Income Coalition could not find one county in the United States where a minimum wage worker, paying 30 percent of his or her income for housing, could afford a one-bedroom apartment.

As for the government rent-subsidies aimed at alleviating the hardship of low-income tenants, those too have shrunk. The war on terror and the war in Iraq have pushed them off the agenda.

Today parts of Renter-World constitute a desperation sector of America. Poor people, crammed into too-small apartments, struggle to pay for food, rent, transportation, and medical care.

To paraphrase Linda Loman, lamenting the plight of her husband, Willy, in ''Death of a Salesman": ''Attention must be paid" to these renters.

The reason is pragmatic.

In the past, Renter-World has been a gateway to Owner-World. Low-income workers, renting for a few years, have saved up enough for the downpayment on a house, and, with scrimping, have kept up with mortgage payments. But today's renters cannot so easily make that leap. The Big Box shelver, married to the fast food waitress, may want the American dream. They may have left family thousands of miles away to seize the dream. But without some housing relief, they will never leave Renter-World.

And the promise of America, the dream for millions of Americans, is to leave Renter-World. That first mortgage -- often the first mortgage for a family -- constitutes step one in the economic mobility we value. High rents trap families, anchoring them on the bottom rung of the ladder that we want them to climb.

For the sake of the renters, and of the nation as a whole, Uncle Sam must pay attention to Renter-World.

Nicolas P. Retsinas is director of the Joint Center for Housing Studies at Harvard University.