it is done on the basis of average of total assets per family. that is what the uploader told me.
though low in number, the marwaris , kayasthas and high caste newars(in lesser extent) literally control nepali economy, so i think thakalis in number 1 surprised me.all those business houses are run by marwaris and each of them is at least 100 million worth. i dont think bahuns or even newars can match them in absolute numbers though they are better represented in bureaucracy and politics.