When Target added a new plus-size line called Ava & Viv last month, it was another sign of a stronger clothing market for larger women.

Plus sizes are on the upswing in women’s retailers and malls. But just as investors keep an eye out for indications of the next downturn, so do shoppers for niche-size clothing, whether big or small, man or woman.

“I’ve seen this movie too many times before. The ending will be the same,” Marshal Cohen, apparel analyst at the NPD Group. “When business gets tough, as it does in recessions, retail shrinks down the less popular businesses and expands the higher-margin categories like shoes, cosmetics or accessories,” he said.

No category in apparel retailing is more volatile than plus-size women’s clothing. And none is more bereft of action than small-size men’s clothing, a niche without a national chain devoted to it. Internet retailing and custom tailors help niche-size buyers find what they need. But the seesawing availability of clothing in nearby stores frustrates many such shoppers.

To specialists in apparel, the focus on the high-volume, average-size clothing by most retailers is no surprise.

“Whether it’s clothes or bikes, retailers put out what sells,” said Alan Au, president at Jimmy Au’s for Short Men 5’8” and Under, the Beverly Hills, Calif., retailer that bills itself as the nation’s only seller of designer clothing for short men.

As the economy grew stronger over the past couple of years, a new cycle began for niche-size clothing.

In recent months, J.C. Penney, Sports Authority and H & M have all added to their store inventories of plus-size clothes for women.Before this most recent uptick, every niche saw its presence narrow in brick-and-mortar stores. Petite women have seen dedicated retail stores disappear, including Petite Sophisticate and Pinstripes Petites stores.

Tall women lost Tall Girl shops, though Long Tall Sally replaced it and many clothing retailers stock taller sizes online.

Most niche sizes are not as profitable as other departments. Plus sizes represent only 15 percent of the total women’s apparel business, which is not a large enough segment to warrant permanent staying power. A long-held stigma is that plus-size women aren’t much into fashion and don’t like clothes. “Nothing could be further from the truth,” said Cohen.

Vicki Senger of Minneapolis was a size 3X for many years. As a retirement plan consultant, she had to dress professionally when she made presentations to potential clients at Ameriprise. But Senger, unlike most plus-size women, had an “in.” Her best friend was a plus-size model and a sales associate at Dayton’s and later Nordstrom. “She knew my body type and knew before I did what would look good on me,” she said.

Senger knew what every other plus-size woman knows: retailers aren’t ordering enough. “Many retailers can’t afford to stock the expanded size ranges on the floor so they offer it online instead,” said Dan Butler, senior adviser at the National Retail Federation and president of Maple Point Consulting.

“When you add sizes you have to sell enough of them. I ran department stores for 20 years and plus-size sales were never as big as we hoped,” he said. “They stock the sizes where they can sell hundreds, not 20.”

Retailers also don’t reorder new styles in plus sizes as often as average sizes. The result is plus-size women visit stores less often because they won’t see something new. Target hopes to avoid that problem with Ava & Viv line by replacing it monthly, similar to Target’s other apparel lines, spokesman Joshua Thomas said.

For short men, the supply-and-demand equation is tilted severely against them. The big-and-tall business is 15 percent to 20 percent of the men’s market, while short is less than 5 percent.

Finding a retailer who specializes in clothes for short men is especially difficult in the Midwest, where men are taller than on the coasts, said Marty Mathis, owner of Marty Mathis Clothiers in downtown Minneapolis.

He sells custom-made suits, sportcoats and pants so that he can fit any guy. But the 5-foot-7 retailer said that buying off the rack is a challenge in the Twin Cities for a shorter guy. Milbern’s in St. Paul has some options, he said.

Elliot Ginsburg, a 5-foot-3 Minneapolis attorney, said it’s “horrible” trying to find shirts, sportcoats and suits locally. He orders nearly everything by phone from Jimmy Au’s, after visiting the California store once to take his measurements. He has to spend more than $100 on a dress shirt and $800 to $1,000 on a suit. “I only have a few of each, but it’s cheaper than buying a lot of stuff that doesn’t fit,” he said.

Although a short man can have sleeves and pants shortened, many choose not to go to the expense. Instead they roll up sleeves and pants when possible. David Hoang of Blaine, who is 5-feet-2½, said he often pulls up the sleeves on his dress shirts to make them look right. “At least plus-size women and big- and-tall men have their own stores. You don’t see a ‘Short and Skinny’ or ‘Short and Chubby’ store in the mall.”

Cohen thinks short men need to apply more pressure to retailers. “Short men don’t like to talk about it,” he said. “Until they become as vocal as plus-size women, they’re going to be pushed to the fringe.”