If you are concerned, then why do you sell 100 year bonds?

WSJ: Finance officials from the world’s largest emerging-market nations are growing increasingly worried that currency turbulence could hurt their economies as the dollar strengthens, Mexican finance minister Luis Videgaray said on Saturday.
“The most recurring concern is the U.S. dollar appreciation,” Mr. Videgaray said in an interview, as global finance ministers and central bankers met in Washington to discuss threats to the world economy.