||This study examines why a growing percentage of Taiwan-born immigrants in the U.S. have identified themselves as Taiwanese rather than ethnic Chinese in the U.S. decennial censuses between 1990 and 2000. The trend appears inconsistent with the assimilation theory, which postulates that ethnic groups will become more detached from ethnic politics and identity the longer they stay in the United States. The application of a double cohort method enables us to separate the period effect from the duration effect, which is critical to analyzing the changes. Results show sharp temporal differentiation and large geographical variation. The older generation of Taiwanese immigrants and recent arrivals to the United States, as well as those who live in Los Angeles, are the most likely to regard themselves as Taiwanese rather than ethnic Chinese. In contrast, Taiwanborn immigrants who have greater English proficiency, who have less education, and who have [mainland] Chinese as their neighbors are less likely to do so. Moreover, age-at-arrival is a key determinant in identity formation and change. Those who came to the U.S. when they were young are least likely to regard themselves as Taiwanese. Over time, Taiwan-born immigrants have indeed become more acculturated. Young Taiwan-born immigrants who came to the U.S. before the 1970s are least likely to make a switch to Taiwanese during the period. However, acculturation alone does not prevent one from claiming Taiwanese identity on the census form. For Taiwan-born immigrants, writing in Taiwanese on the census form appears to be a "rebellious" or "awakening" act and a symbolic expression of solidarity with their compatriots in Taiwan, empowered by a growing sense of Taiwanese consciousness. Globalizationmay now have allowed immigrants to maintain a closer tie with their country of origin than before, especially in times of crisis.