It's inaccurate to say the RICHEST COUNTRIES as stated by Forbes. It's based on "PER CAPITA", meaning PER PERSON. It's easier for tiny countries like Qatar, Singapore, Brunei, Hongkong, or Luxembough to accumulate wealth per person. For bigger and more populous countries, it's much harder.
The richest country based on TOTAL GDP (growth development product), and NOT on PER CAPITA, is the United States, followed by China, Japan, India, Germany etc.. Qatar becomes 56th, Singapore (38th), HongKong (35th), Luxembourgh (93th), Brunei (120th), Laos (128th).