Table 1 Descriptive information of 85,542 twins born 1926–1996 and alive in 2006 originating from 50,507 twin pairs, where 35,035 pairs included both twins, and 15,472 included only one twin.

From: Evidence of large genetic influences on dog ownership in the Swedish Twin Registry has implications for understanding domestication and health associations

  Total (column percent) Not Dog owner (column percent) Dog owner (column percent)
Sample (row percent) 85,542 (100.0) 77,039 (90.1) 8,503 (9.9)
Sex
   Male 39,608 (46.3) 36,689 (47.6) 2,919 (34.3)
   Female 45,934 (53.7) 40,350 (52.4) 5,584 (65.7)
Birth year
   1926–1939 12,703 (14.9) 12,140 (15.8) 563 (6.6)
   1940–1954 23,800 (27.8) 21,388 (27.8) 2,412 (28.4)
   1955–1969 16,959 (19.8) 14,303 (18.6) 2,656 (31.2)
   1970–1984 13,774 (16.1) 12,053 (15.6) 1,721 (20.2)
   1985–1996 18,306 (21.4) 17,155 (22.3) 1,151 (13.5)
County-wide dog density
   <8% 16,413 (19.2) 15,221 (19.8) 1,192 (14.0)
   8–10% 29,530 (34.5) 26,901 (34.9) 2,629 (30.9)
   10–12% 30,271 (35.4) 26,936 (35.0) 3,335 (39.2)
   >12% 9,328 (10.9) 7,981 (10.4) 1,347 (15.8)
Dog breed*
   Mixed breed 2,317 (2.7) NA 2,317 (27.2)
   Golden Retriever 428 (0.5) NA 428 (5.0)
   German Shepherd 389 (0.5) NA 389 (4.6)
   Labrador Retriever 374 (0.4) NA 374 (4.4)
   Dachshund 342 (0.4) NA 342 (4.0)
   Jack Russel Terrier 253 (0.3) NA 253 (3.0)
   Swedish Elkhound 194 (0.2) NA 194 (2.3)
   Cavalier King Charles Spaniel 185 (0.2) NA 185 (2.2)
   Cocker Spaniel 170 (0.2) NA 170 (2.0)
   Border Collie 147 (0.2) NA 147 (1.7)
  1. Note: All variables are statistically significantly different between dog owners and non-dog owners, at p < 0.001 by Pearson chi-square tests. *Dog owners may have had several different breeds. Only most common breeds reported in this table.