a few Nairs and by non-Hindu immigrants, respectively. The Nambudiri Brahmins were at the top of the ritual caste hierarchy and in that system outranked even the kings. They regarded all Nairs as Shudra. Below the Nambudiris came the Tamil Brahmins and other later immigrants of the Brahmin varna. Beyond this, the precise ranking is subject to some difference in opinion. Kodoth has placed the Samantan caste below the Kshatriya rank but above the Nairs, but Gough considers that the Pushpagans and Chakyars, both of which were the highest ranked in the group of temple servants known as Ambalavasis, were ranked between the Brahmins and the Nairs, as were several other members of the Ambalavasi group. She also believes that some Nairs adopted the title of Samantan in order to emphasise their superiority over others in their caste. The unwillingness of the higher varnas to engage in what they considered to be the polluting activities of industrial and commercial activity has been cited as a reason for the region's relatively limited economic development. Keralite traditions included that certain communities were not allowed within a given distance of other castes on the grounds that they would "pollute" the relatively higher-ranked group. For example, Dalits were prohibited within 64 feet. Likewise, a Nair could approach but not touch a Nambudiri. Subgroups The Nairs identify themselves as being in many subgroups and there has been debate regarding whether these groups should be considered as subcastes or a mixture both of those and of subdivisions. There have been several attempts to identify these various groups; most of these were prior to the end of British governance in India but Kathleen Gough also studied the issue in 1961. These analyses bear similarities to the Jatinirnayam, a Malayalam work that enumerated 18 main subgroups according to occupation, including drummers, traders, coppersmiths, palanquin bearers, servants, potters and barbers, as well as ranks such as the Kiriyam and Illam. Although the Jatinirnayam did not itself distinguish any particular subgroups as ranking higher, subsequent attempts at classification did do so, claiming the various occupations to be traditional ones and stating that only the higher ranked groups were soldiers. Anthropologists, ethnologists and other authors believe that the last name of a Nair was a title which denoted the subgroup (vibhagam) to which that person belonged and indicated the occupation the person pursued or was bestowed on them by a chief