While there may be plenty of people buying luxury homes in the next few years, fewer people will be buying new homes, signaling an end to the housing boom of the past five years, a leading housing economist said this week.

William C. Apgar Jr., a professor at the John F. Kennedy School of Government at Harvard University and associate director of the Joint Center for Housing Studies of the Massachusetts Institute of Technology and Harvard, predicted that new housing starts this year will total only about 1.3 million, much lower than last year's 1.62 million figure and below the 1.4 million to 1.5 million projections by various housing and lending trade groups. The reason for the drop is less demand, not fallout from last October's stock market collapse, he said.

"The stock market crash is being oversold as the reason for the volatility in the housing market over the past five months," said Apgar, who was one of a series of speakers here at the U.S. League of Savings Institutions' 1988 Economic Outlook Conference. "So the declines we'll see this year aren't tied to the stock market crash, but they're rooted to the decline in demand."

Apgar said that articles and analyses in November and December that linked the drop in housing starts to home buyers losing money in the stock market were misleading.

"It's true large amounts of wealth disappeared, but most of that was paper wealth," he said. "For most home buyers, the crash was looked upon with passing interest because most of their wealth is in the home they own. Equity is still the largest value of wealth for most Americans."

For the next 10 years, Apgar said, most of the buyers will be baby boomers, who are between the age of 30 and 40, are making more money than ever before and are outgrowing their existing homes. They're looking for more size and better quality, he said. Many of these people bought their homes in the 1970s, have substantial equity in their homes and possibly refinanced their home within the past two years when interest rates dropped to single digits in some parts of the country.

While the number of first-time home buyers between the ages of 18 and 29 will continue to decline, Apgar said, there will be more single-person elderly households. By the year 2000, there will be an estimated 7 million households with a person age 65 or older, up from 4.1 million last year.

There will continue to be an oversupply of apartment buildings, Apgar said. For the third quarter last year, the national average apartment vacancy rate was 8.1 percent, the highest rate in 22 years. But he said he expects many builders to complete their current apartment projects even though they may no longer be as profitable as they were in past years. "They'll take a lower profit and have a lower margin instead of the risk of taking a loss on the time already invested in the project," he said.

In his regional forecasts, Apgar predicted that the Northeast will experience a housing slowdown, particularly since its population is growing more slowly. The trend, he said, is for people in the region to head to the South and the West.

"The high housing costs are making it difficult for employers to attract new employees," Apgar said. "That directly affects population growth."

After several economically gloomy years in the Midwest, Apgar said, the outlook is definitely "brightened." Somewhat improved farm economies and a stable population are expected to help the region's near-stagnant housing market rebound.