In recent weeks, the threat to the farm credit system, the failures of thrift institutions and the weak condition of the commercial banking system have been sources of concern in the government and in financial circles.

Alan Greenspan, former economic adviser to President Ford, told his business clients the other day that, as a result of a tripling of domestic debt in the last 10 years, "The risks to the economy are greater than at any time since the end of the war."

One of the problems, nicely documented by Ohio University Prof. Ed Kane, is that the federal deposit insurance system is geared to the slow-paced 1930s and 1940s and hasn't kept pace with volatile changes in the now intensely competitive financial institutions.

At a recent breakfast with reporters prior to a meeting on this issue sponsored by the American Enterprise Institute, Federal Reserve Board Vice Chairman Preston Martin put it in the bluntest terms.

He said that, by going "for the high risks," some bank and thrift institution managers have placed their depositors and the financial system itself in jeopardy. Their guiding philosophy has been to "say to the saving public or investing public: 'These are all insured; the government's behind these, you know. Put your money in here. We want to play roulette with your money, and it's all safe.' "

Even deposits well over the $100,000 insurance ceiling appear to be safe because the government will not allow any large bank to fail. In fact, since the establishment of the Federal Deposit Insurance Corp., no depositor in a bank with more than $1 billion in total deposits has lost money, an AEI report notes.

Typically, when a big bank gets into trouble, the FDIC has arranged for another big bank to assume all of its liabilities -- including accounts over $100,000. Remember what happened last year when the FDIC and Fed couldn't find another bank to swallow the huge losses of Continental Illinois Bank of Chicago? They pumped $4.5 billion of government money directly into Continental rather than liquidating it -- in effect, nationalizing the bank.

In response to criticism of the way it handled Continental, the FDIC proposed a modified payoff plan that subjects the over-$100,000 depositors to some risk of loss and attempts, thereby, to eliminate some of the favored treatment of large banks compared to small banks.

But Stanley C. Silverberg, director of the FDIC's Division of Research and Strategic Planning, argued at the AEI session that the insurance system has played only a marginal role in the record number of bank failures this year -- more than 100 at this writing.

He blames the bank failures more on the general deterioration of the economic environment -- that is, the changing economic conditions here and abroad that make a bank's balance sheet look bad. He pointed out that, in contrast to the problems of the Federal Savings and Loan Insurance Corp. (which insures deposits at thrifts), the FDIC still has a pool of insurance money of about $19 billion "and, barring a real major, quick collapse of the international side, I think the FDIC's financial position is quite adequate."

Nonetheless, Silverberg endorses one modest idea that is getting increased attention: a variable-rate deposit insurance system under which the FDIC would set premiums based on the riskiness of a given bank's balance sheet.

The FDIC has proposed new rules, incorporated in legislation now being considered by Congress, that would base the cost of its insurance to banks on an evaluation of whether the bank presents a risk that is normal or above normal.

It may be instructive for the average citizen to know that the FDIC calculates that about 1,800 banks, or 13 percent, -- would be judged to be above-normal risks right now. It also would charge problem banks for increased costs if the FDIC has to maintain close supervision of those banks. All told, a bank in the riskier category would pay about four times as much for its insurance as a normal bank, although in absolute terms, the change is not overwhelming -- the premiums rising from one twenty-fifth of 1 percent of deposits to only one-sixth of 1 percent.

The Federal Home Loan Bank Board also has proposed legislation that would allow it to charge higher premiums if a thrift engages in the kind of lending operations that it doesn't like -- such as horse breeding and windmill farms -- rather than home mortgages.

Critics of the FDIC proposal argue that the higher costs are so marginal that they won't make conservatives out of "risk-prone" managers, but only will punish those already in trouble, after the fact. And the FHLBB proposal, some say, is arbitrary and doesn't get to the basic issue of coping with the problems caused by high market interest rates or lousy management.

But the hard reality is that banks and thrifts have suffered huge losses in the last several years, in real estate, in farm and energy loans, and in the Third World. Many of these losses have been covered up.

Martin says, with feeling, that the situation cries out for changes in the statutes so that regulators can get at problem institutions sooner than they do now and not have to prove that they're defunct or insolvent. He also thinks that the industry should establish a self-regulatory agency, analagous to the one operating in securities markets.

Kane and others argue that $100,000 is too high a ceiling for insurance, and that it should be phased down gradually to perhaps $20,000 -- with depositors allowed to buy extra insurance above that amount. Sen. Jake Garn (R-Utah), chairman of the Senate Banking Committee, acknowledges that Congress may have made a mistake in boosting the insurance level to $100,000. But he says that this figure now is politically untouchable.

There will be a day of reckoning if we allow the existing mess to get worse by permitting business as usual. Kane correctly contends that the weakened state of financial institutions is mostly a result of regulatory laxity. The government should get tougher; self-regulation isn't enough. Examiners -- and better quality examiners -- have to respond more quickly to trouble in the banking system.

Right now, the basic FSLIC policy is to permit failing or failed thrifts to survive. Ultimately, they will have to let some of these institutions fail -- and better now than later.