AT SOME events on his book tour, black men have accused Ralph Richard Banks of advocating genocide. In fact, the Stanford professor of family law has merely written a book called “Is Marriage for White People? How the African-American Marriage Decline Affects Everyone”. But abuse is what you get for suggesting, as Mr Banks does, that black women—not only the “most unmarried” group in American society but also the one that least intermarries with other races—should look to white, Latino or Asian men as potential mates. After all, the alternative is often no marriage or relationship at all.

The collapse of marriage among blacks is well documented (see chart), but not the sexual, psychological, emotional and social toll this has taken on black women. Seven out of ten are single. Of the others, many are forced into “man-sharing”. This crisis in the black “relationship market”, as Mr Banks calls it, starts with a “man shortage”. About one in ten black men in their early thirties are in prison. As a group, black men have also fallen behind in education and income, just as black women have surged ahead. Two black women graduate from college for every black man. As these women rise into the middle class, the men stay in the lower class, becoming less compatible. Many black women respond by “marrying down, but not out,” as Mr Banks puts it. But that makes bad marriages. Two out of every three black marriages fail, about twice the rate of white marriages. The real problem is the behaviour of those few black men who are considered good catches. They often stay unmarried for the opposite reason: they have too many options. As one man told Mr Banks: “If you have four quality women you're dating and they're in a rotation, who's going to rush into a marriage?” Even black men who nominally commit to one woman are five times as likely as their white counterparts to have others on the side.

One way or another, many black women thus become, or stay, single (as two of Mr Banks's three sisters are). As one woman tells him: “We focus on our careers, our friends, go back to school, whatever. We fill our lives with other things.” But in the hundreds of interviews Mr Banks conducted, he found pervasive sadness.

The most obvious solution, he discovered, also runs into the greatest taboo: intermarriage. This is ironic, because black men are statistically very open to marrying outside their race—more than one in five does. But fewer than one in ten black women intermarries.

For some black women, a white husband brings bad memories of slavery and Jim Crow. Others have conditioned themselves to find non-black men unattractive (lacking “swag”, in the argot). Still others fear that men of other races find black women unattractive, or that their children might be “not black enough”. But by far the most common reason seems to be that black women still regard intermarriage as tantamount to betraying the race. “My black heart,” says one black woman as she contemplates marrying out, “I would need to turn it in.” “We know it's a struggle,” says another, “but we women got to stand by the black man. If we don't, who will?”