There is no doubt that prejudice against interracial dating has declined over the last several decades, and that the practice has become far more common than it once was. At the same time, as New York Times columnist John Tierney points out in this recent post, a high proportion of the population still has strong preferences for dating people of the same race. Tierney summarizes several recent studies that summarize this perhaps unsurprising finding. One of the most interesting studies quoted by Tierney is this recent analysis of preferences in online dating, which concludes that the same-race preference may be extremely strong:
For equal success with an African-American woman [relative to an African-American man], a Hispanic man needs to earn an extra $184,000 [in annual income]; a white man needs to earn an additional $220,000.
For equal success with a white woman [relative to a white man], an African-American needs to earn an additional $154,000; a Hispanic man needs $77,000; an Asian needs $247,000.
For equal success with a Hispanic woman [relative to a Hispanic man], an African-American man needs to earn an additional $30,000; a white man needs to earn an additional $59,000.
For equal success with an Asian woman [relative to an Asian man], an African-American needs no additional income; a white man needs $24,000 less than average; a Hispanic man needs $28,000 more than average.
The research is extremely interesting (even if somewhat depressing). But there are two potentially important omitted factors that I think should be included. The first is the subject's racial group's percentage of the local population where he or she resides. If the person in question lives in an area where her group makes up 80 or 90 percent of the population, she loses very little by choosing to avoid interracial dating. She still has 80 or 90% of the relevant "market" to choose from. By contrast, if her group is a tiny minority, she is passing up far more potential dating opportunities. This may partially explain why whites and blacks are, on average, more reluctant to engage in interracial dating than members of other ethnic and racial groups, particularly Asian-Americans. Whites and blacks are more likely than Asians and Hispanics to live in areas where their group is either in the majority or at least a very large minority - although we should not forget the greater historical prejudice against African-Americans as well.
The second important omitted variable is the strength of the subject's other preferences in a mate, besides race. The higher your standards for beauty, intelligence, income, social skills, and so forth, the less you can afford to also cut out a large percentage of the dating pool by foregoing interracial dating. The same is true if your standards are hard to meet because they are simply unusual rather than high (e.g. - if you insist that your romantic partner have exactly the same religious or political beliefs, even if the beliefs you hold are uncommon). By contrast, if your other standards are relatively easy to meet, you can probably find a romantic partner even if you are unwilling to date outside your racial group, and you therefore have less incentive to compromise on your racial preferences.
If I am right, then people are more likely to be receptive to interracial dating if they 1) live in an area where their group is a small minority, and 2) have hard to satisfy nonracial standards for their significant other.
UPDATE: A number of commenters note that I may be "ignoring" various other relevant variables such as cultural differences between groups. I did not claim in the post to have identified every relevant variable. I merely noted two that may be very important, but have been neglected in the studies. I also did not claim that ALL reluctance to engage in interracial dating is the result of "prejudice." However, some significant part of it probably is. Cultural differences alone cannot account for the fact that there is much greater reluctance to engage in interracial dating with blacks than with other groups despite the fact that cultural differences between blacks and whites are, on average, probably smaller than those between native-born whites and recent Hispanic or Asian-American immigrants.