Among active Philadelphia voters - those who have voted at least once in the last four years - the state counted about 136,000 whose names and birth dates did not match those with PennDot IDs. Overall, that number is 15.6 percent of the city's active registered voters, about 874,000.
But among older voters, the percentage without PennDot ID increases - to 19.5 percent among voters aged 65 to 79, and 27.4 percent among voters 80 and older.
Under the new voter-ID law, some elderly voters may be able to use other forms of acceptable identification, such as current U.S. passports or photo IDs issued by nursing homes or other licensed Pennsylvania care facilities.
But in Philadelphia and the rest of the state, most older citizens do not live in licensed care facilities, according to officials with the Philadelphia Corp. for Aging and the state chapter of AARP.
To vote, the thousands who don't already have acceptable photo ID will have to assemble various documents and visit a PennDot driver's licensing center at least once.
"These are a lot of people who aren't walking anywhere, so we're very concerned," said Linda Riley, director of communications and legislative affairs for the corporation for aging. "We'll do our best to help people get the ID they need. But there are huge obstacles to surmount, both transportation and also birth certificates, especially for people born outside Pennsylvania."
Another option, for those who can describe themselves as ill or disabled, may be absentee or alternative ballots.
Under the new law, absentee-ballot applications require voters to provide the last four digits of their Social Security numbers, to check against the same information in their original voter-registration applications. But no photos are required to get absentee ballots.
The figures on Pennsylvania voters with and without PennDot ID were first made public two weeks ago by the Department of State, with a county-by-county breakdown that showed Philadelphia facing a bigger voter-ID problem than any other county.
Statewide, the analysis counted 758,000 registered voters without PennDot ID, about 9.2 percent of the state's 8.2 million voters.
In Philadelphia, the state counted 186,830 voters without PennDot ID.
But 50,000 of the total were described as inactive, not having voted within the last four years, and state officials speculated that many were former students or others who no longer lived in the city.
Among active voters, the state counted 136,182 without PennDot ID, about 15.6 percent of the city's 874,000 active voters.
Late last week, the state provided city election officials with a list of individual voters whose names did not match those with PennDot ID. The list made it possible, for the first time, to flesh out the voter-ID problem with details like voter ages and party registrations.
In Philadelphia, Democrats accounted for 108,746 of the active voters without PennDot ID, compared with 15,694 Republicans - a slightly greater ratio than the Democrats' overall voter registration edge of more than 6-1.
It's difficult to quantify, but several factors suggest the numbers may overstate, at least slightly, the scope of the ID problem.
If an individual used a different first name on his voter-registration form than on his driver's license, for instance, it would come up as a non-match. But the driver would still have a photo ID that would probably pass muster.
The list suggests that some non-matches resulted from alternate spellings of the same last names. For instance, there are more than 10,000 non-matches of names beginning with the letters "Mc" followed by a space. Someone with the surname McHugh, hypothetically, could have it spelled "Mc Hugh" on his voter-registration record.
If PennDot's practice is to spell "McHugh" without a space and the Department of State always spells it "Mc Hugh," every McHugh would register as a voter without PennDot ID.
The Inquirer has requested similar data for counties besides Philadelphia, but the Department of State has not yet provided it.
Contact Bob Warner at 215-854-5885 or firstname.lastname@example.org.
Inquirer staff writer Miriam Hill contributed to this article.