On April 29, 2010, the United States Navy authorized women to serve aboard submarines. Previously, objections such as the need for separate accommodation and facilities (estimates that modifying submarines to accommodate women would cost $300,000 per bunk versus $4,000 per bunk on aircraft carriers) had prevented the change. The Navy stated that larger SSGN and SSBN submarines had more available space and could accommodate female officers with little/no modification. Qualified female candidates with the desire to serve were available. (Women then represented 15 percent of active duty sailors and were earning about half of all science and engineering bachelor's degrees.)