this article is from WeChat official account: < span > Gu Yu data - Tencent News (ID: guyudata) < / span > < a > < span >, author & amp; data analysis: Li Jingyi * Lin Ying * & nbsp; Jiatangya, design: Chen Ming *, editor: Chi Er, (* a member of the co copyright Fenghuo digital news team), the original title: "big cities don't have" 30 ", they need to work harder even to give birth to children", head photo source: Beijing meets Seattle