 In the 1990s, Yamagata created official art works for a celebration of 200 years of emigration to America (1990), the Freedom Campaign in Berlin (1990), the 500th anniversary of Columbus's first visit to the New World (1991), the 3rd IAAF World Championships in Athletics, Osaka (1991), the Barcelona Olympics (1992), Kyoto 1200 year celebration (1992) and the Atlanta Olympics (1995).At the prompting of Beat poet Allen Ginsberg, Yamagata started giving poet Gregory Corso a monthly stipend in 1992, which allowed Corso to live comfortably for the rest of his life.He held a solo exhibition at Mexico City National Museum of Art in 1990 and participated in a "Very Special Arts" charity art event in 1993.