http://blog.american.com/2012/04/the-obama-jobs-gap-is-up-to-15-million-missing-jobs/ Under normal circumstances, there would be 153,000,000 jobs, including parttime jobs that people hold voluntarily. Currently, however, the number of full-time jobs and those who are holding part-time jobs voluntarily stand at 138,189,000
Furthermore, this assumes zero growth in the working capable population, so even if the necessary 15 million jobs were restored in America, unemployment would be higher than 2007 by simple nature of population growth.