At the same time, more than 1 million Afghan refugees migrated to the city during the 1980s and '90s, many of them linked to the drug trade in their homeland. The hard-line attitudes among some of these refugees also fed into a vicious gangland-style power struggle between Sunni and Shiite Muslims for control of the city's religious institutions.
Like many here, Yusuf blames Karachi's troubles on the international community, which, he says, abandoned Pakistan and the region after Soviet troops pulled out of Afghanistan in 1989.
"We were stupidly compassionate people [to take in so many Afghan refugees], and Karachi is paying the price," Yusuf said. "The world let us down."
Unlike many here, however, Yusuf decided to do something about the increase in crime.
He founded a nongovernmental organization called the Citizens Police Liaison Committee in 1989 to marshal private sector resources to help law enforcement agencies fight waves of kidnappings. The committee bought computers and other equipment that the police otherwise could not have afforded.
In an interview Monday, Yusuf insisted that the Pearl case does not constitute a resurgence of kidnappings. He and others also note that the apparent kidnapping is different from most snatches here, which are carefully choreographed affairs.
"Police put out feelers through their street informants or even precinct-level politicians to determine who has the victim and that he is safe," said Khan, the Herald editor. Then they signal it is time to negotiate, often via a brief newspaper article describing the family as "anxious to hear from the kidnappers."
In time, a sum is paid, the victim is released, and the kidnappers flee. "Karachi kidnappings have been nonviolent and always were about money," Yusuf said.
In some instances, kidnappers take on a Robin Hood dimension, especially in working-class neighborhoods of a city where the income disparity between rich and poor is vast. There, people have come to view abductions as a kind of gunpoint socialism, with the rich giving to the less affluent kidnappers.
While the people of this violence-prone city have expressed shock at the Pearl case, they are equally appalled by the death threats and the chaotic, often contradictory string of e-mails directed not to the police or the journalist's family but to Western and Pakistani news media.
"It has the air of a group that's not quite clear how to do it," noted Khan, "like the work of a bunch of amateurs."
Pakistani law enforcement officials, now assisted by the FBI, seem uncertain how to read both the death threats and the kidnappers' vague demands. In interviews, senior police officials base their cautious optimism about Pearl's eventual fate at least in part on the assumption that the kidnappers must be after money and therefore want to keep him alive.
Yusuf, who saw the journalist the day before he vanished, said there was another cause for optimism--an electronic relationship Pearl had formed with Bashir Ahmed Shabbir, the alleged intermediary.
"He'd built a rapport in corresponding with Bashir by e-mail," Yusuf said. "They'd even talk about domestic things, like the fact his [Pearl's] wife was sick.
"To this man, Daniel was a person who had a wife," Yusuf added. "That gives me hope he's still alive."