Table 1

Covariates in the generalised additive models

Tobacco control scoreCategorical term for tobacco control score for England. 4 categories: 24.5, 27, 48 and 51
Cigarette costlinessWeighted average price of packet of 20 cigarettes in month of interview divided by average monthly gross income of respondent (ie, proportion of monthly income that a packet of cigarettes costs). Include as cubic regression spline
Number of adults in the householdNumber of adults in households of OS respondent. Include as linear term
AgeAge of OS respondent. Include as cubic regression spline
GenderCategorical term for gender of OS respondent
Government office regionCategorical term for government office region of residence of OS respondent. 9 categories: East Midlands, East of England, London, North East England, North West England, South East England, South West England, West Midlands and Yorkshire & the Humber
Social classCategorical term for national statistics socioeconomic classification (NS-SEC) of OS respondent. 4 categories: managerial and professional occupations, intermediate occupations, routine and manual occupations, not classified
EmploymentCategorical term for employment status of OS respondent. 3 categories: employed, unemployed, economically inactive
EducationCategorical term for highest level of qualification that OS respondent has received. 8 categories: degree level qualification (or equivalent), Higher educational qualification below degree level, A-Levels or Highers, ONC/National Level BTEC, O Level or GCSE equivalent (Grade A–C) or O Grade/CSE equivalent (Grade 1) or Standard Grade level 1–3, GCSE grade D-G or CSE grade 2–5 or Standard Grade level 4–6, Other qualifications (including foreign qualifications below degree level), No formal qualifications
IncomeTotal gross income from all sources before deductions for income tax, National Insurance etc. Include as a cubic regression spline
  • OS, Opinions and Lifestyle Survey.