Since he took to standing on the corner, he's had six sidewalk interviews and has handed out more than 100 resumes. Some passers-by, including accountants, lawyers and big-time execs, have stopped to chat with Mercer - known on the street as "the job-sign guy" - or to buy him food or pay for his parking.
But he's still unemployed.
" 'All I want is a job,' " he recalled telling several people who stuffed money down his chest pocket. " 'Just give me a job, somebody.' "
Having exhausted his unemployment benefits and no longer looking for work in traditional ways, Mercer is among the 57,700 Philadelphians whom authorities call the "hidden unemployed" because they aren't counted in the official unemployment figures compiled and released by the government.
When added to the city's latest official unemployment figure of 67,300 for June, that makes 125,000 Philadelphians - or 19 percent of the labor force - listed as "underutilized," officials say.
Paul Harrington, director of Drexel University's Center for Labor Markets and Policy, said the statewide underutilization rate - including people who are unemployed and those who have given up searching for work but still want a job - is 13.9 percent.
"Are these big numbers?" Harrington asked. "Yes, but given the magnitude of the recession, not surprising. This is an area that was not adding jobs, like the Southwest and the Rocky Mountains.
"Kids without a college degree are really having a hard time. People 55 or above are moving into teen jobs. If you went to the grocery store 10 years ago, you would not see anyone 60 years old in there."
In June, the city's 67,300 unemployed residents represented 10.2 percent of the labor force, tied for second-highest in Pennsylvania with rural Cameron County, the "Land of the Endless Mountains" - and behind only Pike County in the northeast corner of the state, which had 10.7 percent unemployed. By comparison, the statewide unemployment rate was 7.5 percent in June, and the national average was 7.6 percent.
"The job market is coming back, but not as fast as we thought," said Mark Edwards, president of Philadelphia Works, an agency supported by government and private funding that connects employers with job seekers and provides training. "The demand is so high, and more and more companies are in a situation where they post a position and within days or hours they have exceeded the ability to process responses."
The number of people out of work in Philadelphia is actually higher than unemployment numbers show, experts say, because unemployment rates only reflect people out of work who are searching for jobs, and not those who have given up.
"This is the big misnomer," Sallie Glickman, senior adviser at the Fels Institute of Government, said of the official unemployment figure. "It's actually never been an accurate number. In Philadelphia and other cities, the discouraged numbers are really high."
Sherell Robinson, 25, of South Philly, was not eligible for unemployment compensation because the jobs she held were temporary. She has been looking for a full-time job for more than 18 months. She has applied for hundreds of jobs, resulting in just one interview.
"It's like [employers are] not biting," she said. "That's discouraging."
Robinson has an associate's degree in criminal justice and is pursuing a bachelor's degree at the University of Phoenix campus in Center City. She does some work in real estate, is an occasional seamstress, worked recently as an intern for City Councilman Kenyatta Johnson and gets by on excess school financial-aid funds. She's raising a 4-year-old daughter and has considered leaving her hometown, hoping the job market might be better elsewhere.
In fact, more than 190,700 Philadelphians travel to the suburbs for work because the city's four largest areas of employment - Center City, University City, Temple University and the Navy Yard - are not "large enough or expanding fast enough," according to a Center City District report released last year.
So much for retiring
Beverly Brice, of West Philadelphia, should be looking forward to retiring in three years, kicking up her feet and enjoying life after decades of working. But Brice, 62, finds herself devoting many hours a week to staring at a computer screen, filling out job application after application.
"I get so afraid when I have to fill out an application and I have to list the year I graduated from high school," said Brice, who got her diploma in 1968. "I don't let that stop me. If I find something that interests me, I apply."
Brice has been out of work since she was laid off from the insurance firm AIG in 2011 after the service department was shuttered. She had worked there for seven years.
"It's been rough," she said. "It could be worse."
When her unemployment compensation ended in May, she began to have a hard time paying her mortgage, but later worked out a deal with the bank for a lower rate. She survives on her pension and with the help of family.
But for those who have been unemployed long-term, that means they "can't save money, no retirement and no benefits," said Tim Styer, project developer with the Philadelphia Unemployment Project, an organization for the poor and unemployed.
Beyond that, the chances of getting a job become radically slim after long bouts of unemployment, according to a soon-to-be published paper in the American Economic Review described briefly in the Wall Street Journal earlier this month. Researchers found that the callback rate drops dramatically after nine months of unemployment. Interview requests for medium- and low-skill jobs dropped by 20 percent, although the same was not true for positions that required a college degree.
'An American problem'
"We have a job-creation problem," said Drexel's Harrington. "It's not a Philly problem or a Pennsylvania problem - it's an American problem."
The national unemployment rate in July was 7.4 percent - the lowest since the 2008 economic crash. An estimated 162,000 jobs were added to the U.S. economy, but Wall Street had expected 184,000, not including the farm sector.
Experts say the job market has had uneven progress, with positions increasing in the service sector including professional, health care and education. And in Philadelphia, where only 23 percent of residents have a bachelor's degree or higher, some folks may get left behind.
"In Philadelphia, we have a lot of jobs that require some college or higher," said Edwards, of Philadelphia Works. "We have job seekers who don't have that level of skill."
Philadelphia Works provides training for those job seekers, but federal cuts this year meant $700,000 less and 200 fewer training slots. Edwards is hoping to win some grant money to make up for the cuts.
Suffering the most in Philadelphia's unemployment picture are minorities, immigrants, the least-educated, college graduates and ex-offenders, according to a report released by the Philadelphia Jobs Commission earlier this year.
To give companies an incentive to create more jobs, the city in 2002 passed a law implementing a job-creation tax credit. It gives eligible business owners a onetime credit of up to $5,000 for each new, qualified full-time job. Since last year, when the tax credit was increased from $1,000 to $5,000, at least 10 companies have applied, promising to create more than 550 jobs. Tax credits of up to $10,000 also are available for businesses that hire ex-offenders.
"We believe there needs to be some incentive, and part of it is to do the right thing," said Councilman Wilson Goode Jr., who sponsored the bill. "When you have significant portions of the population unemployed, it places the city at an economic disadvantage."
Meanwhile, back at 19th and Market, Mark Mercer was thrilled two weeks ago when he thought he had found a new job - but it didn't materialize. With his two St. Bernards, Stanley and Oliver, he began bunking down in his 1994 Ford Tempo.
Despite it all, Mercer remains optimistic.
"My life is in God's hands," he said. "I'm going to be fine. I believe something good is going to happen."
On Twitter: @Jan_Ransom