The best estimates of a maximally accurate source would be very frequently updated and follow a random walk. And authoritative sources like WHO are often said to be our most accurate sources. Even so, such sources do not tend to act this way. They instead update their estimates rarely, and are especially reluctant to issue estimates that seem to “backtrack” on previous ones. Why?
First, authoritative sources serve as a coordination point for the behavior of others, and it is easier to coordinate when estimates change less often. Second, authoritative sources need to signal that they have power; they influence others far more than others influence them. Both of these pressures push them toward making infrequent changes. Ideally only one change, from “we don’t know”, to “here is the answer”. But if so, why do they feel pressures to issue estimates more often than this?
…authoritative sources prefer a strong consensus on what are the big sources of info that force them to update. This pushes for making very simple, stable, and clear distinctions between “scientific” info sources, on which one must update, and “unscientific” sources, where it is in considered inappropriate to update. Those latter sources must be declared not just less informative, but uninformative, and slandered in enough ways to make few tempted to rely on them.
Due to the third of these pressures, authoritative sources will work hard to prevent challengers competing on track record accuracy. Authorities will issue vague estimates that are hard to compare, prevent the collection of data that would support comparisons, and accuse challengers of crimes (e.g., moral positions) to make them seem ineligible for authority. And other kinds of powers, who prefer a single authority source they can defer to in order to avoid responsibility for their decisions, will help to suppress such competitors.
Here is more from Robin Hanson.