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Thursday, July 19, 2018

No proof required: Numbers don’t lie-people do

‘If you tell a lie big enough and keep repeating it, people will eventually come to believe it’: Goebbels.

Written by Surjit S Bhalla | Updated: September 5, 2015 12:05:31 am

In ‘Census, Christians, Conversions’ (iexp.in/GCc186342, The Indian Express, August 29), I made three major points on the recently released census data on religion. First, that contrary to the wild interpretations of the data by Hindu fundamentalists, population growth among Muslims was converging to the Hindu rate. Second, that the pace of Muslim population growth was largely a function of their relative income status and had precious little to do with religion. Third, that given the known determinants of population growth, the only explanation for the constancy in the share of the Christian population between 1991 and 2011 (2.32 and 2.3 per cent, respectively) is largescale conversion to Christianity. One simple method of estimating the annual rate of conversion was to assume that the Christian population growth should be similar to that of Sikhs; the difference between this estimate and the actual Christian population growth is an estimate of the annual conversion rate.

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A tragic consequence of the omniscience of social media is that writers seem to care more about the support they get on Twitter than the veracity, or logic, of their arguments. In ‘Bend it like Bhalla’, (iexp.in/nrb186352, The Indian Express, September 1) Tony Joseph seems to have fallen into this familiar narcissistic trap — let facts (numbers) be damned, because I am not really concerned with the truth, and more concerned with Warhol’s 15 minutes of fame.

He accuses me of manipulating the data (and worse!) to obtain the conclusions I “desire”. Since he only comments on Christian conversions, and not my comments on Muslim population growth, I am assuming that Joseph is in agreement with my “bending” of data to obtain the politically correct conclusion on Muslims — or does he think that Muslim population growth is as worrisome as alleged by Hindu fundamentalists. Joseph needs to come clean on this.

The critical, almost definitional, explanation of “natural” population growth is fertility. Populations can increase due to more births, fewer deaths, net immigration and conversion. Most religions have a broadly similar death rate, and a very low (relative to the population) net immigration rate. Hence only two factors — fertility and conversion — explain a large proportion of differences in population growth. But Joseph is unable to face the all-too-well-known reality of Christian conversions. This “blinder” makes him score several successive ducks in his analysis. A partial list follows.

Duck 1: “It takes skills of a high order to create and raise a red flag over a population percentage that is stable”. What Joseph is referring to is the fact that between 1991 and 2011 the fraction of the Christian population stayed almost as constant as the Northern Star — it was 2.32 per cent in 1991 and 2.3 in 2011. Note that a constant population share implies a strict equality between community and national population growth. What is curious is that the Christian population share between 1971 and 1991 declined by 0.29 percentage points. So what caused the share to stay constant between 1991 and 2011 — or alternatively, what caused Christian population growth to accelerate from 1.39 (1971-91) to 1.93 per cent a year (1991-2011)?

Per capita income, education of women, and fertility rates all suggest that the growth rate should be declining. Perhaps the Christian death rate (relative to the average Indian) has declined by enormous proportions? Very unlikely and there is no evidence to support this inference. Perhaps a lot of foreign Christians are now resident Indians? Not possible. This leaves conversion as the only explanation.

Even if the erroneous assumption is made that Christian population growth between 1991 and 2011 is the same as in the earlier two-decade period, one obtains a rate of 1.4 per cent per annum. One additional fact: the rate of growth of the Hindu population declined from 1.97 (1971-91) to 1.81 per cent (1991-2011). So there is little reason to assume that Christian population growth should not decline by at least the same magnitude. If one assumes that, then the expected Christian population growth rate for 1991-2011 is 1.39 minus 0.16, or 1.23 per cent a year — not far from my assumption of 1.22 per cent.

Duck 2: “It is a well-known and academically accepted fact that skewed sex ratios like this [as among Sikhs] have a significant impact on population growth”. This is the most glaring example of appealing to the Twitterati, and I challenge both Joseph (and my own paper The Indian Express!) to show me one study that shows that, all other things being equal, a skewed sex ratio significantly affects population growth. Just one study, and it need not even be published.

The effect of fertility levels and adult sex ratios was analysed for 15 major states of India, for the period 1981-2011. This revealed, as expected, that fertility levels are strongly related to population growth — and that there is no relationship between sex ratios and population after controlling for fertility.

Duck 3: If the Duck 2 test is not convincing for Joseph, let us conceptually test the assumed relationship between sex ratios and population growth. Assume the initial population is 100 for all communities. Reflecting the adult sex ratio (15-39 years) of 1991, one obtains 49 male Christians and 51 female Christians; for Sikhs, the sex composition is 51 males and 49 females (sex ratios of 1,030 for Christians and 955 for Sikhs). The excess Sikh males do not marry; excess Christian women do marry and produce Christian kids. Hence, one has 51 Christian women producing kids compared to 49 Sikh women. Each woman produces the same number of kids, and there are no deaths. This simple accounting exercise yields 147 Christians in 2011, compared to 145 Sikhs, that is, the average annual Christian population growth rate is higher by 0.06 percentage points.

Duck 4: Perhaps the most glaring, egregious example of numbers not lying, but people doing so, is Joseph’s reference to the “rock steady” share of the Jain population at 0.4 per cent in 1991 and 2011. The actual numbers are 0.41 per cent in 1991 and 0.37 per cent in 2011; rounding up, one obtains a constant 0.4 per cent share! The population (log) growth rate of Jains during this period, 1.47 per cent per year; the national average, 1.97 per cent per year. To repeat, a constant share implies a strict equality in growth rates. Is 1.47 equal to 1.97? Only lying numbers, nee individuals, will give you that result.

Golden Duck (when a batsman is out on the first ball): Joseph goes through convoluted logic trying to score runs, and the contortions cost him his wicket on the first ball. He takes the growth of the Hindu population in the US (8.3 per cent a year) and concludes that according to present trends, Hindus will constitute 52.6 per cent of the US population in 60 years. The Hindu growth rate in the US is high because of immigration, not fertility, and definitely not conversion. And why does Joseph want to wait 60 years to “prove” his damned lie? Just assume that the US allows in a third of the Indian Hindu population tomorrow, and he can obtain a Hindu majority in one day (actually three months because of inadequate airplane capacity).

The writer is contributing editor, ‘The Indian Express’, and senior India analyst, the Observatory Group, a New York-based policy advisory group

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