In the past six months the economy has been on a roller coster. Still booming at the beginning of the year, industry plunged into recession in the spring. Unemployment shot up, consumers stopped spending, retailers' sales plummeted and industry's profits slumped.

At least that's what happened nationwide. But what about in Washington? This recession has been notable for its patchiness. Autos, housing and steel have been hit much harder than other industries.

And the old industrial areas in the antion have suffered much more from the economic downturn than have other areas with newer industries, less dependence on manufacturing and more people employed in government or service industries.

The District and surrounding metropolitan area is the prime example of a local area whose economy is insulated from the ups and downs experienced across the nation, because it is heavily dependent on government rather than on industry.

The business cycle does not lead to lay-offs among bureacrats, ambassadors or congressman as it does among auto workers. Unemployment in the metropolitan area was 4.9 percent of the work force in June, according to the latest figures from the Bureau of Labor Statistics -- compared with 7.8 percent nationwide, nearly 12 percent in Toledo and 14.2 percent in Decatur, Ill.

The relative security of Washington workers feeds through to the rest of the local economy. Since fewer people lose their jobs or their overtime payments here than in many other parts of the nation, so Washington retailers, restaurateurs, car salesman and other business people suffer less of a falloff in business than their counterparts in Detroit or Toledo.

The Washington Post's regional index of the economy aims to measure the ups and downs in the local economy. It has been published since April in Washington Business and has been calculated back to the end of last year.

So it covers the period when the national economy slid into recession in the spring and when the recession began to ease up over the summer. After dropping a little in January, the regional index then picked up in February and March before falling back in April May and June as recession hit.

It has shown clear signs of recovery since then. Although still below the best levels of December and February, the last week has seen a substantial pickup.

The index has moved much less overall than the national economic indicators, such as the government's figures for industrial production and retail sales. It is almost certainly true that business and industry in the Washington area have suffered less of a fall in output than the average across the nation. But the size of changes in the index cannot properly be compared with the national indicators, since the regional index is a composite measure.

Nationwide, the recession really began to bite fiercely in April, although industry began to cut back its production a couple of months before that. In February and March industrial output fell by 0.2 percent and 0.5 percent, respectively, while the regional index showed small gains.

In April, May and June the national picture worsened sharply with falls in industry's output of between 2 1/4 and 2 3/4 percent in each month.

The Washington index dropped a little in each of those months.

But whereas the regional index began to recover last month, national industrial production went on dropping -- albeit at a slower rate.