RT Article T1 Happiness begets children? Evidence for a bi-directional link between well-being and number of children JF The journal of positive psychology A1 Kim, Jinhyung A2 Hicks, Joshua A. LA English YR 2015 UL https://krimdok.uni-tuebingen.de/Record/1912570599 DO 10.1080/17439760.2015.1025420