What is the burden of producing evidence in a Title VII retaliation case?

In Title VII retaliation cases, once the plaintiff has established a prima facie case, the burden of production shifts to the defendant to articulate a legitimate, nonretaliatory explanation for its decisions.... [Once the defendant meets this burden,] the legally mandatory inference of retaliatory discrimination arising from the plaintiff's prima facie case drops away.... The burden of production [then] shifts back to the plaintiff to show that the alleged explanation is a pretext for impermissible retaliation. This burden thus merges with the plaintiff's ultimate burden of persuading the court that he is the victim of retaliation.

Yartzoff v. Thomas, 809 F.2d 1371, 1376-77 (9th Cir.1987) (citations omitted).