One of the untenable arguments against reservation is to question the Mandal estimation, by projection from the 1931 census and drawing on the National Sample Survey Organisation’s survey for 1999-2000, that 52 per cent of population belongs to backward castes (BC). The charge was led by Karan Thapar as Devil’s Advocate in his May 21 interview of Union HRD Minister Arjun Singh and in his article ‘Mandal Muddle’. Others have followed, breezily asserting in their ignorance of historical facts that “no votary of caste-only-criterion is anxious to update these figures.”The crucial historical fact missed by anti-reservationists is that BC commissions and other bodies have been pressing for inclusion of BC-related population data over the last half-century. Anti-reservationists have just woken up to this, with the sole Canutian aim of rolling back the inexorable wave of reservation.NSSO’s sample survey cannot be a substitute for or supersede census, current or old, so far as quantifying, as close as possible, the total population and of any section, including BC population. Otherwise, why should India and other nations persist with censuses when a less-expensive and sample survey method would do for estimating population.Therefore, the Mandal methodology of projection from the latest available census, is more acceptable and closer to ground reality than sample surveys, which may help in other ways, such as understanding details of many quantifiable and measurable variables between social, economic, and other classes.There is evidence to show the limitations of the NSSO’s methodology. For example, its surveys of 1999-2000 and 2004-05 show STs in Punjab, Haryana, Delhi and Chandigarh (partly corrected in the latter round) where no STs are recognised by the presidential orders. Similarly, the survey showed SCs in Nagaland, where there are none. One important reason for these aberrations is that classification of social groups by NSSO was entirely based upon the household head’s declaration.The effect is that the methodology produces great deviation for BC population, because BC listing is very recent at the Central level (1993) and in northern states. Many BC persons are unfamiliar with it. This is compounded by the slowness of listing by some states. That is why West Bengal’s BC percentage is as low as 6.2 per cent, which is unlikely considering the much higher percentages in neighbouring states.In the identification of BC Muslims (specific castes and tribes of all religions, including Islam and Christianity, have always been included in BC and ST lists), the NSSO’s figure of 31.7 per cent in 1999-2000 and partly corrected to 40.7 per cent in 2004-05 is much lower than reality.For example, how can it justify 56.8 per cent for Muslim OBCs in 1999-2000 going down to 52.7 per cent in 2004-05 for Karnataka when, as noted by Sachar, Karnataka, like Kerala, has included the entire Muslim population as a sub-category of BCs and the Central List has excluded only nine castes/communities of Muslims who are not socially backward. The wide variations between the two rounds are evidence of the yet incomplete process of correction of NSSO’s errors. This is also true of the NSSO’s overall BC figure tom-tommed by Karan Thapar and others. When errors are eliminated and maximum precision is introduced, the figure will rise to that estimated by Mandal.The matter can be settled once for all only by an up-to-date census. The situation needs an immediate special census operation, without waiting for 2011. Evasion of this necessity cannot be visited upon the BCs by seeking to deny them their right to reservation.Such a census will require careful preparation. I can provide all guidance gratis. The census will have to encompass castes in all religions because the caste system is a social reality even for converts. With figures obtained from such a census as a base, the NSSO’s sample survey of social, educational and economic variables, will bring out the stark differences between the backward and forward castes. When such a census is undertaken, Karan Thapar and others are not likely to have the last laugh. In any case, all these controversies are misplaced because whether BC population is 36 per cent or 52 per cent, it does not make any difference to the reservation quota of 27 per cent, which Mandal recommended in deference to a Supreme Court direction in the Balaji case (1963), capping total “vertical” reservation at 50 per cent, the reservation for SC plus ST already being 22.5 per cent.(The writer is an adviser to the Union HRD ministry.)