NEW YORK ( TheStreet) -- In the chart above, J.P. Morgan biotech analysts Geoff Meacham and Cory Kasimov make another argument for why the biotech bull market should continue to run higher. Price-to-earnings multiples for large-cap biotech are on the rise, but that's okay because so earnings growth is also accelerating. The sector's P/E expansion that began in early 2012 has gone almost parabolic in 2013. Take a look at the near-vertical slope of that blue line, with P/Es for stocks like Celgene ( CELG) , Gilead Sciences ( GILD), Amgen ( AMGN) and Biogen Idec ( BIIB) approaching 20 and poised to move even higher into the second half of the year. Is the biotech multiple expansion a concern? The J.P. Morgan team thinks not because the 2012-2015 compounded annual growth rate for biotech earnings is forecast to reach 18%. Right now, the projected 2015 P/E for large-cap biotech is 14-16x. It may be hard to believe, but revenue and earnings expectations for this year are still on the low side. Check out the slide on the next page.