Offman, Judith
Pesola, Francesca
Sasieni, Peter
Article History
Received: 2 November 2017
Revised: 5 February 2018
Accepted: 7 February 2018
First Online: 22 March 2018
Competing interests
: The authors declare no competing interests.
: The data set used here can be obtained from the PHE Office for Data Release. The authors can provide data specifications for any data requests to the Office of Data Release.