bottom out        
phrasal verb with bottom verb uk/ˈbɒt.əm/ us/ˈbɑː.t̬əm/
 到达最低点;不再恶化
to have reached the lowest point in a continuously changing situation and to be about to improve
  Economists think that the recession is bottoming out. 经济学家宣称经济衰退即将走出最低谷。