During the past two or three decades, the nature of the Washington metropolitan area has changed markedly. There has been growth in the private sector and a change in the region's composition -- factors that eventually will define the "personality" of the area just as the federal government did in the past.

The percentage of area residents employed by the federal government has decreased from approximately 40 percent in the 1950s to approximately 20 percent today. Between July 1983 and July 1984, 89 percent of the more than 55,000 new jobs in the region were in the private sector.

You see this change in the new corporate names appearing in the region, especially around Tysons Corner, the I-270 corridor and other developments that are marketed as "technology centers." The companies are young, high- growth, technology-based, often publicly owned businesses. Many enjoyed at least their initial growth from U.S. government contracts for research and development services. These so- called "high-tech" businesses made up nearly half of The Post's most recent list of the 100 largest businesses in the area.

According to the Greater Washington Research Center, there are now some 1,230 "technology-based" firms located here, employing more than 110,000 people. By comparison, the "Silicon Beach" or "South Coast" area of California, which The Los Angeles Times recently described as "booming," has a maximum of 160 high-technology companies employing about 13,600 people.

Many of these companies have played significant roles in local affairs. They also are finding an organized forum in the Greater Washington Board of Trade's task force on high technology, led by John Toups, chairman and president of Planning Research Corporation.

The first visible indication of the task force's contribution to the Washington region was a program called "Edutour," organized in concert with the Washington Area School Study Council, which represents the superintendents of the region's 15 public school systems. This was an opportunity for senior-level executives of these technology-based corporations and the managers of the local school systems to educate each other.

For two days, there was open, candid dialogue; suggestions for cooperative ventures; and concrete agreements from individual businesses to assist individual school systems. As this spirit grows, these corporations collectively will contribute more and more resources to public schools and, perhaps, to private schools, colleges and universities.

Such involvement, however noteworthy, is only a hint of the emerging role of high-tech business here. As businesses have grown in the region and as new, similar businesses are attracted here (largely as the result of the area's business development campaigns), their role in local affairs increases. Their executives become better known as local opinion-shapers.

These organizations are, in one way or another, involved in information: its management, development, analysis, applications and communication, as well as its processing by computers and by humans, and the ways businesses can use it to produce business opportunities. So rather than categorizing them as "high-tech" businesses, it would be more appropriate to think of them as "third wave" businesses in terms explained by Alvin Toffler.

As they grow individually and collectively, these businesses will increasingly define our area, just as the automobile industry defined Detroit and -- until recently -- the business of government almost exclusively defined the Washington area.

Other communities may have more technology-based businesses in absolute numbers, but it is unlikely that any metropolitan area will have as high a percentage of its total economic base made up of such businesses. In this sense I believe Greater Washington will become the world model of what a "third wave" metropolitan area should be like.