title: Methods used to estimate the size of the owned cat and dog population: a systematic review.
abstract: BACKGROUND
  There are a number of different methods that can be used when estimating the size of the owned cat and dog population in a region, leading to varying population estimates. The aim of this study was to conduct a systematic review to evaluate the methods that have been used for estimating the sizes of owned cat and dog populations and to assess the biases associated with those methods.A comprehensive, systematic search of seven electronic bibliographic databases and the Google search engine was carried out using a range of different search terms for cats, dogs and population. The inclusion criteria were that the studies had involved owned or pet domestic dogs and/or cats, provided an estimate of the size of the owned dog or cat population, collected raw data on dog and cat ownership, and analysed primary data. Data relating to study methodology were extracted and assessed for biases.
  
  
  RESULTS
  Seven papers were included in the final analysis. Collection methods used to select participants in the included studies were: mailed surveys using a commercial list of contacts, door to door surveys, random digit dialled telephone surveys, and randomised telephone surveys using a commercial list of numbers. Analytical and statistical methods used to estimate the pet population size were: mean number of dogs/cats per household multiplied by the number of households in an area, human density multiplied by number of dogs per human, and calculations using predictors of pet ownership.
  
  
  CONCLUSIONS
  The main biases of the studies included selection bias, non-response bias, measurement bias and biases associated with length of sampling time. Careful design and planning of studies is a necessity before executing a study to estimate pet populations.
authors.affiliation: Centre for Evidence-based Veterinary Medicine, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, LE12 5RD Loughborough, UK. martin.downes@nottingham.ac.uk
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Downes
authors.forename: Rachel S
authors.initials: RS
authors.lastname: Dean
authors.forename: Jenny H
authors.initials: JH
authors.lastname: Stavisky
authors.forename: Vicki J
authors.initials: VJ
authors.lastname: Adams
authors.forename: Douglas J C
authors.initials: DJ
authors.lastname: Grindlay
authors.forename: Marnie L
authors.initials: ML
authors.lastname: Brennan
mesh_terms: D000818:Animals; D015982:Bias; D002415:Cats; D004285:Dogs; D004812:Epidemiologic Methods / Q000662:veterinary; D006801:Humans; D010067:Ownership / Q000706:statistics & numerical data; D057805:Pets