It seems to me that not all people called experts actually are. In fact, there are whole fields in which none of the experts are experts. But let’s try to define terms.
You might say that an expert is someone who knows more about a subject than some random dude off the street. That could mean that the man in street typically had false ideas [worse than a coin toss] about the subject, while the expert admits that he knows nothing, but let’s aim higher. We’ll define expertise as something that not everyone has, that gives you at least some predictive value (possibly a lot), and sometimes the ability to control outcomes. Such real expertise can be proven experimentally. Generally, that kind of expertise can be acquired (the wisdom of the Occident), but it may be that not every one is talented enough to be very good at it.
Then again, by a different but occasionally useful definition, an ‘expert’ is someone that society considers an expert, whether he actually has any predictive power or not. We denote that social position by quotes.
Sometime no-one has any any predictive ability: some stuff, nobody understands. There’s a good chance that we will still have some some socially-approved ‘experts’ on that subject.
You can have a situation in which expertise exists in some field exists – there is a knowledge set that can confer predictive value, and at least some people have that knowledge – while the people generally considered experts by society (‘experts’) are useless, or worse than useless. You can even have situations in which virtually everyone – except for the ‘experts’ – has expertise on a subject. You can have negative time trends: things go from a situation in which virtually everyone knows certain facts to one in which the overwhelming majority of people – including the ‘experts’ know things that just aren’t so.
There are plenty of examples. At the high point of Freudian psychoanalysis in the US, I figure that a puppy had a significantly positive effect on your mental health, while the typical psychiatrist of the time did not. We (the US) listened to psychologists telling us how to deal with combat fatigue: the Nazis and Soviets didn’t, and had far less trouble with it than we did.
Fidel Castro, a jerk, was better at preventive epidemiology (with AIDS) than the people running the CDC.
In the 1840s, highly educated doctors knew that diseases were not spread by contagion, but old ladies in the Faeroe Islands (along with many other people) knew that some were.
In 2003, the ‘experts’ ( politicians, journalists, pundits, spies) knew that Saddam had a nuclear program, but the small number of people that actually knew anything about nuclear weapons development and something about Iraq (at the World Almanac level, say) knew that wasn’t so.
The educationists know that heredity isn’t a factor in student achievement, and they dominate policy – but they’re wrong. Some behavioral geneticists and psychometricians know better.
In many universities, people were and are taught that really are no cognitive or behavioral differences between the sexes – in part because of ‘experts’ like John Money. . Anyone with children tends to learn better.
Along these lines, I’ve read Tetlock’s book, Expert Political Judgment. A funny, funny, book. I will have more to say on that later.