At least 170,000 people live in such dwellings in Hong Kong, according to Policy 21, a research unit tasked by the government to take stock of the situation. Such housing can be found all over the city, in units fenced off with plasterboard or cagelike wire mesh, carved out of apartments that once housed a family each but that have since been subdivided multiple times. This subdividing of privately owned apartments is legal as long as safety and sanitation requirements are met.

“It is quite hard to know how many there are,” said Sze Lai Shan, who works for the Society for Community Organization, a nongovernmental organization that campaigns for social equality. “We hear about them from the people we work with — they tell us of new flats that have been subdivided or old ones that have closed down.”

While tiny housing of this kind has existed in Hong Kong for many years, it has expanded as soaring property prices have pushed more and more low-income earners out of the market for regular housing in recent years. Rent on these spaces has risen nearly 20 percent in the last four years, and now gobbles up about a third of the residents’ incomes, a report released by Ms. Sze’s organization this month showed. On a per-square-foot basis, the spaces cost at least one-third more to rent than regular apartments that are not subdivided, which average about 22.70 Hong Kong dollars, or $2.93, a square foot per month.

“It is very expensive to live here, so I have to be more frugal, and I cut my food expenses,” said Yuen Luen-yuk, 49, who moved to Hong Kong from Zhanjiang, on China’s south coast, eight years ago and has a low-paying job looking after the residents at a home for people of retirement age.

Her living space, with a ceiling too low for an adult to stand, is part of a subdivided apartment in the neighborhood of Kwun Tong. Nine other people live there; they share a dim kitchen, a basic bathroom and a narrow corridor cooled by humming electric fans.

“I’ve not thought about renting something better,” Ms. Yuen said, “because that means all your salary will be given to the landlord.”

Hong Kong’s housing situation is now one of the reasons the government of Leung Chun-ying, who took the helm of the city’s administration last year, is deeply unpopular. Mr. Leung has pledged to add 20,000 units a year to the city’s already large stock of social housing for low-income earners.