A picture, they say, is worth a thousand words. This infographic at The American Society for Cell Biology's ASCB Post is worth at least that many and probably more, graphically depicting data on the careers of Ph.D. biologists from the 2012 report of the Biomedical Workforce Working Group of the National Institutes of Health and other sources, including our own 2012 postdoc survey.
More vividly and concisely than mere words could do, the infographic answers the question, "Where will a biology Ph.D. take you?" Short answer: Most likely to a postdoc, but only rarely—about 15% of the time for current postdocs—to a tenure-track academic job. Other common destinations include nontenure-track academic posts and "non-research, science-related jobs." If the data occasionally seem inconsistent—29,000 equals 15%, for example, while 25,000 is 20%—that should be forgiven, since the data come from different sources and the available data aren't that good overall, as Jessica Polka, a postdoc in cell biology at Harvard Medical School, acknowledges in her introduction.
Until better data are available, this is the best information of this sort that you're likely to find. There's reason to hope that better data is forthcoming, however. The National Academies Committee on Science, Engineering, and Public Policy is expected to release soon the sequel to the report that started the postdoc-reform movement, "Enhancing the Postdoctoral Experience for Scientists and Engineers." "Hopefully, clear data on these job markets will empower trainees to make better-informed career decisions," Polka writes.