Despite this range of estimates, the number 6 million is the one that tends to appear in popular accounts and political debate. This has something to do with what Matthew White calls "a very real human tendency to exaggerate":
Let's face it. Big numbers are impressive, and there's a very real human tendency to exaggerate. While lurking on Usenet discussions of historical atrocities, I've seen plenty of outrageously large claims (accusations of Pol Pot killing 10M, which is more than the number of Cambodians living at the time; accusations of international Communism killing "billions", which comes close to being more than the number of people who have ever lived under Communism.) and far fewer outrageously low ones. Even the most infamous exceptions to this tendency, the Holocaust Deniers, shouldn't blind us to the fact that exaggeration (slight exaggeration) occurs in the Holocaust numbers. Most scholars put the death toll between 5 and 6 million, but most popular accounts emphasize the high end alone -- 6 million.6 million is also the approximate number of children under five who die every year throughout the world, mostly from preventable causes, according to UNICEF’s report Progress for Children 2015, which can be downloaded on this page (see also the related press release). That’s roughly 16,438 deaths per day, 685 per hour and 11 per minute.
Sad though these figures are, they also reflect the enormous progress that has been made throughout the world in reducing child mortality, according to the 2014 report Level and Trends in Child Mortality, which on page 9 provides the following information:
A baby born today has a dramatically better chance of living to age five compared with one born in 1990. The global under-five mortality rate dropped 49 percent, from 90 (89,92) deaths per 1,000 live births in 1990 to 46 (44,48) in 2013 (table 1). Over the same period the total number of under-five deaths in the world fell from 12.7 million in 1990 to 6.3 million in 2013 (table 2). Put another way, 17,000 fewer children died each day in 2013 than in 1990—thanks to more effective and affordable treatments, innovative ways of delivering critical preventive and curative interventions to the poor and excluded, and sustained political commitment. These and other vital child survival interventions have helped save about 100 million lives since 1990.The approximate number of children under five who died in 1990, 12.7 million, is roughly equal to the number of non-combatants who lost their lives to criminal actions of Nazi Germany and its European allies during World War II, according to my estimates.
Much has improved since 1990. Much remains to be done.