Although critics of the DOE contend that the doctrine unduly inhibits competition, surprisingly, we show that often the degree of competition is unaffected by the presence or absence of the DOE. The inventor can block competition in the absence of the DOE by investing in refinement and drafting broad patent claims. We call this “preemptive” refinement because its sole purpose is to preempt competition. Preemption tends to be socially harmful because the inventor controls the embodiments in E and F under either regime; and society loses the value of the refinement costs paid by the inventor to deter competition in the regime without the DOE.