It is hard to find method in the madness of the Pol Pot regime, but French-American academic Patrick Heuveline can at least shed light on the data. A professor of sociology at the University of California Los Angeles, Heuveline has been number crunching in Cambodia since he first arrived in the country in 1992. As a UN demographer, he was responsible for voter registration in Kandal province in the run-up to the 1993 election.

After returning to the United States, Heuveline went back to school for his PhD after deciding to make a career out of researching Cambodian social trends. Among his most cited research is his work on determining the actual death toll of the Khmer Rouge regime, which he says is indeterminable but possible to narrow down to a range of less than one million. To reach his number, he ran the various death toll estimates through 10,000 simulations that combined the numbers with other demographic variables, such as migration, to test their plausibility.

Since 2000, Heuveline has also conducted research on family changes in the aftermath of the Khmer Rouge regime. His most recent project, which he has been working on since 2008, attempts to determine the long term effects of losing one or both parents during the Pol Pot years. To do so, his team has routinely interviewed around 60,000 people in Kampong Cham, Kandal and Kratie provinces. By comparing the life outcomes of orphans to their foster parents’ biological children, Heuveline hopes to gain some idea of the damage done to orphans of the Khmer Rouge.

With university out for the summer, Heuveline is in Cambodia to consult with his Cambodian colleagues. He spoke to Bennett Murray about the challenges of applying statistical analysis to Cambodia’s tragic modern history.

The Khmer Rouge death toll varies drastically depending on who you ask. What is your estimate?

The usual range is 1.2 million to 2.6 million with 95 per cent confidence. But it’s so huge, it almost has no value.

In my view, there is a 75 per cent chance that the death toll falls between 1.5 million and 2.25 million, with a 15 per cent chance that it is higher and a 15 per cent chance that it is lower.

Other researchers have made very specific estimates with great variation, with Michael Vickery estimating only 700,000 and the Cambodian government estimating 3.3 million. Why the discrepancy?

There’s a couple you can rule out, like the government surveys because they were not conducted very scientifically. They tried to interview everyone in the provinces and have people testify as to how many people in their families they lost, so there’s the obvious issue of double counting. And in some provinces, they tried to count everyone who died in the three years, eight months and 20 days that the Khmer Rouge were in power, and in other cases they used different dates.

With Vickery also, I can see there are probably some things in there that push the envelope a little bit. He used the 1962 census as his basis, and while there’s nothing wrong with looking at censuses– it’s a very good method– you have to estimate the number of births and deaths from other causes than the Khmer Rouge, and that is very noisy. Even before the Khmer Rouge, we didn’t have very good demographic data. Maybe women were having seven children on average, maybe five, and that creates a very big difference.

How did you come to your estimate?

We have all these numbers and they all have plausibility. So I took all those numbers and I ran 10,000 different simulations to test their reliability. If I find a number only once, it has a 1 in 10,000 per cent chance of being accurate. But I can never rule something beyond any doubt, there is always some probability.

Between the Cambodian Civil War and the US bombing campaigns, Cambodia was not peaceful before 1975. How does that factor in?

That’s another factor of uncertainty. You have to estimate the level of mortality in 1970. How many deaths can you attribute to the bombings of Eastern Cambodia, if you say the number was maybe 300,000 or someone says only 200,000 right there is a gap of 100,000, and you can’t really decide between the two. You compound all these factors of uncertainty, you get this huge range, and I can’t really say anyone on either side of the range is right or wrong.

At least with calculating death tolls, you are seeking a quantifiable sum. How do you determine the social impact of the Khmer Rouge?

With the death toll, it’s a zero/one thing. A person died at that time, or they didn’t. But the social consequences are a bit more open-ended. On face value it makes sense that the Khmer Rouge legacy created all these social ills, because the country was left in a very poor state in 1979. But you had prostitution in Cambodia in the 1960s, and there is HIV in other countries in the region.

In social sciences, when you try to assess the effect, you need a comparison group. You need to find people who are similar except for that particular experience. This is very difficult to do, and this is why I’m often sceptical of the claims of the Khmer Rouge having this and that consequence, because we don’t really know what the common factors are. What would have happened otherwise?

In our current project, we have discovered the proportion of people who have lost at least one parent – 25 per cent. ​But we are still entering the data, and we have no hard facts yet.

What specific results might you find from the orphan studies?

Any child is dependent on adults for his or her access to resources. So the effect of losing a parent is several fold– one, the child is impacted himself in stability functions, the other effect is that the child is adopted by another family and his connection to adult caretakers might possibly be weakened. That is an open question that I am curious to see is the case with Cambodia.

We did conduct some interviews with parents that asked who would be the most natural foster parents for their children were they to die. Most said they would prefer that the children go with the grandparents first, with uncles or aunts second. But we know that families were separated under the Khmer Rouge, so maybe parents went to whoever was in the vicinity in the village. So it’s more open than in other contexts.

What I’m also interested in looking at is if people who were not biological children had different marriage prospects, because we know that parents were usually responsible for marrying their children and were trying to get the best matches. And also the issue of land property, whether orphans will get as much from the foster parents.

If you believe evolutionary theory, it will tell you that parents privilege their biological children. I am not entirely convinced, but we will see if there is evidence that it is the case in Cambodia.