Whenever anyone talks about "bad economics" these days, most people think first of the White House and the Capitol. And small wonder. After all, it's the president and Congress who decide economic policy in this country -- for better or for worse.

But there are plenty of examples of "bad economics" to be found in other parts of the Washington metropolitan area as well -- specifically, the District Building, the Maryland and Virginia state capitols and the city halls of many surrounding communities.

State and local governments yearly enact dozens of provisions that seem like sure-five vote getters, intended to protect the public, but actually end up backfiring on voters in the longer run. Ironically, many of these are portrayed as measures designed to help the poor.

Some classic examples:

Usury Ceilings: Want an easy way to win points with voters? Just enact a state usury ceiling -- particularly on home mortgages loans. From time to time, lawmakers in Maryland, Virginia and the District of Columbia all have succumbed.

There's no doubt the move has strong political appeal, particularly in poor neighborhoods. After all, banks and mortgage companies often are seen as money grubbers. Why not crack down on them? Limit the interest they can charge -- and, presumably, end banks' "gouging" as well.

The problem is, while the move may seem like dynamite politically, experience shows the imposition of interest-rate ceilings is more apt to blow up in voters' faces than actually to zap the banks -- indeed, if it ever has much effect at all.

The reason is that, contrary to many voters' perceptions, interest rates aren't some nasty business practice. They're a price -- just like those charged by carpenters or shoe-repair shops -- determined largely by how much it costs the banks and mortgages companies to borrow money.

If you impose a ceiling on carpentry work that prevents the carpenter from making a profit, the prospects are that he'll stop taking on new jobs at all and shift to another line of work. In the case of banks or thrift institutions, the mortgage money just dries up.

What the politicians frequently do is exploit the issue twice by first imposing the mortgage-interest ceilings initially and then -- when interest rates hit the limits and loans dry up -- claim credit again by voting to remove the ceilings. (Maryland, for example, recently was forced to eliminate its 10 percent mortgage limit.)

On the surface, the move seems virtually costless. The only people who get hurt are the few who are caught trying to borrow when mortgage money becomes scarce. On the other hand, economists also agree there's only one group that really gains: the politicians.

Rent Controls: Here's another popular consumer crackdown that ultimately backfires on the people it's supposed to help.

By itself, the notion sounds like just what the government ought to be doing to protect its citizens: Stop those greedy landlords from raising rents! The District had such legislation on the books for years. And it did help keep rent levels down.

But -- like interest-rate ceilings -- the controls have another effect as well: They alos make it unprofitable for buildings owners to maintain and repair their structures.

The result: In the face of potential losses, landords quickly allow their apartments to run down. Some buildings turn into slums. And many landlords abandon the business entirely. Who's the winner in that case?

TENANTS' RIGHT LAWS: There's no doubt that some landlords abuse their tenants, that some are negligent and uncaring, and that some are even unscrupulous in their dealings. Often, renters have legitimate complaints that deserve a government hearing.

But the District has enacted a set of tenant laws that, in the view of many economists, goes overboard in taking the side of tenants on some issues, and ultimately is threatening to shut poor renters out of apartments. Analysts say many landlords already have shifted to upper-income markets, where they believe there is less risk of landlord-tenant problems.

For example, experts say the present law makes it all but impossible to kick a tenant out -- even if he is ripping up your property. And even if you can get an order to evict an errant tenant, the procedure is mind-bogglingly complex. "I'm surprised," one insider says, "to see anyone wanting to rent housing here at all."

THE COMMUTER TAX: This backward-logic proposal is killed every few years or so, but it keeps coming back -- and understandably, at first blush. The proposal has everything an elected official ever wanted: It raised oodles of new revenues. And you can tax the other guy to get there.

The argument used by proponents seems logical at first: Those who work in the city use D.C. services -- the fire department, police and so forth -- during office hours and they ought to have to help pay for them. A commuter tax, on that basis, seems only to be fair.

But the fact is, studies already have shown that commuters pay more than their share of taxes. First, the out-of-towners often work for companies that pay business taxes to the District. And the commuters themselves contribute to the local economy. Many eat lunch in D.C. restaurants, and buy goods in D.C. stores. In both cases, they pay sales taxes on these transactions.

What imposing a tax does is mostly to rally commuters who work in D.C. to heighten pressure on their employers to move their firms out of town.

D.C. CHARITABLE DEDUCTION: Like the federal income-tax code, the D.C. income-tax law allows taxpayers to claim deductions for contributions to charities -- a defensible-enough sort of writeoff, by traditional tax-code standards.

But symbol-minded officials have added the hitch that the charity must largely benefit the District. If you go to church across the Maryland or Virginia line, for example, you technically can't deduct what you give every Sunday.

The restriction may seem arguable politically -- Let's force these people to channel money to District-based charities, you say -- but it's apt to be viewed as unfair, and even petty, by large numbers of District taxpayers, who contribute to out-of-town charities and colleges.

Few other states have any such limitations.

METRO FARES: As chronicled previously by Washington Post staff writer Douglas B. Feaver, the area's complex metro fare system is an economic and social nightmare, largely because of conflicting social policies among jurisdictions.

The District, for one thing, insists on subsidizing riders, no matter what. Fares are kept deliberately low -- much lower than experts say they should be to keep them in line with rising costs. Virginia wants to cover all costs exactly. Maryland falls somewhere in between.

As a result, metro riders are faced with a complicated fare structure that requires a computerized, magnetic-strip-reading farecard system and includes such paradoxes as forbidding transfers from bus to subway while allowing them from subway to bus.

Metro also has spawned some zany economic policies by local communities outside the subway entrance as well: Some jurisdictions hve tightened zoning to prohibit the development of shopping areas and high-density dwelling units around Metro entrances needed to make the system pay.

THE GROSS RECEIPTS TAX: The District has imposed a levy on banks that taxes them on their gross receipts. That ought to zap the banks, you say! Especially the big ones that dominate the city's financial community.

The problem is, by taxing gross receipts (rather than income or sales volume), the levy hits smaller banks harder, often forcing them to pay more in taxes than they earn.

POUPOURRI: Maryland has a law on the books that requires the major oil companies to divest themselves of local gasoline stations they may own. Economists concede it may seem worthwhile politically to zap the oil companies again, but all this does is forstall competition -- and work against the consumer.

The Maryland Senate also considered another anti-competition measure last year, but this time thought twice before enacting it. The bill would have allowed established auto dealers to block the opening of a rival dealership within 10 miles of their present lots.