China has witnessed rapid fertility transition since the 1970s and the transition process has been largely attributed to the rapid socioeconomic development and strict family planning policy. Recent studies suggest that family planning policy has launched the transition process and driven it predominantly during the years before 1990, while socioeconomic factors play a more significant role in the process since the 1990s. By employing the provincial level data, this study finds that the effects of both fertility policy and socioeconomic factors may have declined in the late transition stage. And it finds evidence that the fertility transition is self-sustaining and diffusive, once it is initiated by both socioeconomic factors and policy. <<