There's always unfinished business. In its final weeks, the Carter administration disgorged piles of reports and studies -- a paper agenda for a second term that never came.

Among that heap, you will find a forbidding document entitled "Geographic Restrictions on Commerical Banking in the United States," which recommends that restrictions against interstate banking be dropped. It merits study not because it's gripping reading but because it illuminates the thin hypocrisy of much Washington policy-making.

The issue here goes beyond banks to that more mystical phenomenon, "productivity." This is simply the sum total of the way we collectively handle our affairs; it means getting more out of existing labor, land and investment. But it's become a new religion. So fervently do politicians extol productivity that you reasonably might expect that Congress would do anything to increase to it. Not so.

So long as productivity remains an abstraction, it's wonderful. But in the real world, any time you attempt to get at particular inefficiencies, you inevitably discover they're wrapped in a thick cocoon of vested interests and old habits. Banking -- and the Carter administration's banking report -- simply become a metaphor for this larger contradiction.

Moving money around is part of what's loosely known as the service economy. Americans deal less and less in cash and more and more in cash substitutes: checks and, more recently, plastic cards. In an increasingly affluent and inflationary period, people are more conscious of the value of their savings. They shift their money more frequently.

Doing this job efficiently -- or inefficiently -- is one of the many things that affects productivity. Today we have a bewildering variety of banking institutions: 14,000 commercial banks, 4,700 savings associations, 22,000 credit unions and 450 mutual savings banks.

Expansion of this system in the past 20 years has gobbled up enormous amounts of people, land and money itself. Branching by banks, savings associations and credit unions has been phenomenal; the number of bank branches has more than tripled since 1960 to 36,000 in 1979. Employment in the economy's financial-service sector has doubled since 1960, rising twice as fast as the overall increase in the labor force.

The next time you wait in line to deposit or withdraw money, you might ask whether the system is working as well as it might. On further reflection, you also might wonder whether the huge number and variety of institutions really serve any useful purpose.

What now seems desirable is a gradual shrinkage in the number of banking institutions and an end to the old compartmentalization. The days are long past when it made sense fo savings associations to make only mortgage loans. And electronics promises to make money transfers -- paying bills and making deposits and withdrawals -- more efficient. Machines may substitute for paper, people and buildings.

Given the intensity of the rhetoric for productivity, you might suppose that Congress has been hell-bent on promoting efficient banking. It hasn't. The catch is that virtually no one sees banking issues as having anything to do with productivity. Small banks want to protect themselves against big banks. Savings associations have defended federal interest-rate ceilings on savings deposits because government regulations give the savings associations an interest-rate advantage over banks.

Consequently, Congress is caught up in feudal wars among rival baronies. This sometimes creates its own inefficiencies. Congress' protracted attempt to maintain interest-rate ceilings simply resulted in the creation of new financial institutions -- money market mutual funds -- that satisfied the public's thirst for a realistic return on its money.

All this is changing, but Congress is being dragged along by events instead of forcing the pace. The self-evident futility of trying to maintain interest-rate ceilings promoted legislation last year phasing them out. At the same time, Congress narrowed the legal differences among banks, savings associations and credit unions. For instance, all have received the power to offer interest-paying checking accounts (NOW accounts).

But artificial restrictions remain. The specific prohibition addressed by the Carter administration's report prevents banks from moving across state lines; BankAmerica Corp. can't open branches in New York, nor can Citicorp open branches in San Francisco. This becomes more important now because the advent of new technology and freer competition for savings will threaten some weaker banks and savings associations.

The political temptation will be to protect these weaker institutions, in part by preventing the added competition of interstate banking. It's easy to raise the specter of national dominance by a few big banks; Americans suspect concentrated power, and this is a stong appeal. It's also mostly rubbish, as the Carter report points out.

Over the past 30 years, the overall economic power of banks has diminished. Pension funds and savings associations have grown enormously. Banks' proportion of loans and investments made by all financial institutions has dropped from nearly 60 percent at the end of World War II to about 40 percent now. And in states with powerful big banks (New York and California), small, well-managed banks have continued to flourish.

Permitting interstate banking would speed the introduction of new technologies and encourage rate competition. Weaker institutions, most of which don't face insolvency, would be merged into stronger banks and savings associations. Strong local and regional banks would face new competitors and be forced to adopt competitive technologies and interest rates. It's proproductivity.

And it's not very popular. Predictably the Carter administration report hasn't been received warmly on Capitol Hill. This is not really a partisan issue -- the hypocrisy spreads thickly among both parties.

Some day the restrictions against interstate banking will fall, but Congress ought to be rushing toward change, not crawling.