More than 20 percent of Detroit is blighted and it will take almost $1 billion to fix it. Those are the two major findings of the city’s blight task force, which released new figures Tuesday. Of 380,000 parcels in Detroit, 84,641 are blighted, among which are 73,035 residential structures, like houses. No wonder: The city lost more than 1 million residents in the past 60 years. The group said it would take $850 million to repair neighborhood blight, but as much as $2 billion to remove all of it. The feds have already made $456 million available for cleanup.