The latest figures are published in PLOS Medicine in an article entitled "Mortality in Iraq Associated with the 2003-11 War and Occupation".
The survey conducted in 2011 is based on 2000 randomly selected households who were asked about births and deaths in their family since 2001. All adults in each household were asked about deaths of siblings.
A purpose was to compare the death rate post 2003 with the rate in the 26 months before the war and thereby work out the excess of deaths after the invasion. Previous studies had not looked at what happened after 2006 when the war was in full swing.
It remains unclear how far this type of study can be conducted in a country like Iraq in which government institutions had been degraded by sanctions since 1990 and all figures are suspect. Working out the death rate depends on assumptions about Iraq's population which is not precisely known but is estimated to be 33 million.
The study says the researchers "had to rely on outdated census data [the last complete population census in Iraq dates back to 1987] ... The researchers are 95 per cent confident that the true number of excess deaths lies between 48,000 and 751,000 - a large range".
The survey is complicated by the large migration of Iraqis in 2006-2008 when many fled to safer parts of their own country and up to a million took refuge in Syria while others fled to Jordan and Egypt. The survey estimates an extra 56,000 deaths were not counted due to migration.
There were great differences in comparative safety in Iraq during the decade in which the US had troops in the country up to the end of 2011. The northern three Kurdish provinces were stable and safe and violence was less continuous in the Shia south of the country.
Sectarian violence between Sunni and Shia was at its worst in Baghdad, the mixed Sunni-Shia districts around the capital and mixed provinces like Diyala. Violence between the occupation forces and the Iraqi insurgents was at its most intense in these areas but also in Anbar, the vast Sunni province in western Iraq.
In the battle for Fallujah in November 2004, 2000 insurgents and civilians may have been killed by the US Marines.
The most convincing figures for Iraqi deaths by violence come from Iraqi Body Count (IBC) which looks at the number of people killed in verifiable incidents. In an analysis of over 31,500 incidents in the 10 years up to March 2013 it says that between 112,017 and 122,438 civilians died. That's in addition to the deaths of 39,000 combatants and a further 11,500 civilians whose deaths have been revealed by Wikileaks' publication of the American War logs. This would bring the full total of dead to 174,000 documented as being killed by violence in Iraq since 2003.
The height of the slaughter was during the sectarian civil war between March 2006 and March 2008 when 52,000 people were killed. The number killed has risen over the past year with 5000 dead since April and 258 killed so far this month.Independent