The U.S. dollar has appreciated against every Group of 10 currency this year. It’s done even better on a longer-term basis, with the Bloomberg Dollar Spot Index rising as much as 16% since May 2021 -- a massive move for a developed-economy currency. Naturally, betting on gains in the greenback has acquired a huge following, even among retail investors, gaining a cult-like status almost equal to the self-described “apes” that cheerlead for meme stock AMC Entertainment Holdings Inc.