It was also concluded that this may show that penis size overall affects sexual satisfaction since women chose between the two options they were given.A study published in 2002, conducted at Groningen University Hospital, asked 375 sexually active women (who had recently given birth) the importance of penis size. The results showed that 21% of women felt length was important and 32% felt that girth was important.A study conducted at the Australian National University, published in early 2013, showed that penis size influences a mans sex appeal, and the taller the man, the bigger the effect. The study showed 3D computer generated images at life-size, altering the height and other physical attributes, with women typically registering preferences in under 3 seconds. A preference for taller mens larger penis size was indicated. A US study published in 2015 of the stated preferences of a panel of 75 women using 3D-printed models as scale references showed a preferred penis length of 16 cm (6.3 inches) and a preferred circumference of 12.2 cm for long-term sexual partners, with slightly larger preferred sizes of a length of 16.3 cm (6.4 inches) and circumference of 12.7 cm for one-time sexual encounters. According to the study, however, when asked to estimate the length of their partnerss penis, most women would say a size significantly smaller than what their partner was recorded to be. This suggests that perception of size is not entirely accurate. The visual impression of the size is not necessarily in correlation with the feeling in the vulva and vagina.
A 2005 study reported that "there is no scientific background to support the alleged oversized penis in black people".A study of 253 men from Tanzania found that the average stretched flaccid penis length of Tanzanian males is 11.5 cm (4.53 inches) long, smaller than the worldwide average, stretched flaccid penis length of 13.24 cm (5.21 inches), and average erect penis length of 13.12 cm (5.17 inches).A 2016 study of 248 Korean men identified the average erect penis length to be 13.53 cm (5.33 in). A study of 115 men from Nigeria found that the average flaccid stretched penis length of Nigerian males is 13.37 cm (5.26 inches) long, which is near identical to the worldwide average, stretched flaccid penis length of 13.24 cm (5.21 inches) and average erect penis length of 13.12 cm (5.17 inches). A 2014 American study by Herbenick et al. of 1,661 sexually active men involving Asian American, Black American, White American, Pacific Islander/Hawaiian, and Native American men, found average 
racial differences in erect penile length and circumference to be generally less than one centimeter, with averages in length being: 14.14 cm (5.56 inches) for Asian Americans, 14.66 cm (5.77 inches) for Black Americans, 14.88 cm (5.85 inches) for Pacific Islanders/Hawaiians, 12.86 cm for Native Americans (5.06 inches), and 14.18 cm (5.58 inches) for White Americans (And in circumference: Asians 12.10 cm, Blacks 12.29 cm, Pacific Islanders 11.88 cm, Native Americans 11.36 cm, and Whites 12.25 cm).