It's been a bad week in the United States: six nights of protests, huge anger, rioting and looting in 50 cities, hundreds arrested or injured -- but only six dead over the police murder of George Floyd. The number may have gone up by the time you read this, but it's definitely not 1968 again.
In the last sustained series of riots about police violence against African-Americans, it was very different: 34 dead in the Watts riots in Los Angeles in 1965; 26 dead in Newark in 1967; 43 killed in the Detroit uprising later the same summer. And 46 dead after the assassination of Dr Martin Luther King Jr in 1968, although police violence was not the immediate cause that time.
Does the much lower death toll in 2020 mean that things have got (slightly) better in the intervening half-century? Or does it just mean that wearing bodycams is making the police more cautious about using extreme violence?
Either way, race relations in the United States are still worse than almost anywhere else.
American police are remarkably violent compared to those in other countries, of course. On average, US police officers kill about one thousand civilians a year, whereas British police kill two. The US population is five times the British, but that still means that American police kill civilians at about one hundred times the British rate.
More to the point, in this context, is the fact that about 30% of American civilians killed by the police are African-Americans, although they are only 13% of the US population.
This disparity repeatedly leads to a debate in the US media about whether the disparity is due to racism or just to a higher black crime rate, but it's really quite unnecessary. All you need to know is that the proportion of those killed by the police who were unarmed is two-and-a-half times higher for blacks than for whites.
Which brings us to the nub of the matter: fear. White fear born of ancestral guilt, in turn a heritage from the centuries of slavery.
I live in a racially diverse part of inner London, and I'm familiar with similar districts in Paris, Toronto, Rome and other Western big cities. There's one phenomenon I've never seen there that I have often witnessed in quite prosperous parts of American cities – the Upper West Side, say, or Berkeley – and that is a white couple crossing the street to avoid encountering young black men on the same side of the street.
This is not to be compared with the entirely rational fear of police violence that young African-American men feel, but it is a significant fact: many white Americans believe, consciously or subconsciously, that African-Americans are intrinsically dangerous. The only other place I have run into this phenomenon is Brazil.
There is a saying in Brazil: Branco correndo? Campeão. Preto correndo? Ladrão. If it's a white man running, he's a champion; a black man running is a thief. It is no coincidence at all that Brazil is the only other white-majority country where African slavery was a major domestic institution.
Slavery died out in Europe after the fall of the Roman Empire, although serfdom and other less oppressive institutions persisted. And the Islamic empires didn't care what colour the slaves were: the Turks got as many white slaves from the annual raids into Russia as black slaves from the trade routes across the Sahara and up the East African coast.
This whole institution was essentially alien to the European explorers making their way down the west African coast 500 years ago, but the African kingdoms were quite happy to sell slaves to them too.
The Europeans were equally willing to buy, because they had a use for slaves in the new plantations they were creating in the Americas. Justifying these transactions to themselves required a little psychological adjustment, however, because buying and selling other human beings had not been part of their culture for a thousand years.
They solved their dilemma by deciding that the African slaves they bought were an inferior sort of human being, and that rationalisation permeated the cultures of the slave-owning societies in the Americas for the next four centuries.
The last to give slavery up were the United States, in 1865, and Brazil, in 1888.
But that rationalisation is still hanging around, together with the underlying knowledge that American whites had done their black fellow-citizens a great harm, and the widespread belief among whites that you must fear those whom you have wronged.
It's a witch's brew that blights the lives of African-Americans, and it is taking a very long time to evaporate. There is racism elsewhere too, but most of it is fear of the unfamiliar, directed at recent immigrants, and you can expect it to go away in a generation or two. Alas, this is different.
Gwynne Dyer's new book is 'Growing Pains: The Future of Democracy (and Work)'.