In response to an earlier research paper of mine analysing change in children's time use in the UK (Mullan, 2019), which bore the same title as this book, the following tweet was posted on the social media platform Twitter:

Most of the tweet is a direct quote from the paper's abstract, but the first five words struck me immediately as going to the very heart of something I was tackling in my research on change in children's time use. Take the example of homework. Few would argue that children are not spending more time doing homework today than in previous decades, but in the course of my research I could find no published data or research that showed clearly that children's time doing homework had increased in the UK. In fact, there was scarcely data at all on the time children in the UK spent doing homework. To take another example, it has surely reached the status of truism to state that children today spend less time playing outdoors than in the past. There is comparatively more evidence to support this, but it would fail to meet standards applied to any serious question about adult time use. Mayer Hillman and colleagues’ famous study of change in children's independent mobility has a good claim to have had a deep influence in supporting the view that children's time outdoors decreased from the 1970s onwards (Hillman et al, 1990). This study, however, makes no direct reference to any measure of how much time children spend outdoors. In fact, they are explicit in stating, for example, that there exists no survey evidence ‘about the amount of time children spend playing in the streets’. (Hillman et al, 1990: 78) The key indicators they use to infer change in the time children spend outdoors are licences granted to children, such as being allowed to come home from school alone or go to places other than school alone.