Estimates of the casualties from the Iraq War (beginning with the 2003 invasion of Iraq, and the ensuing occupation and insurgency and civil war) have come in several forms, and those estimates of different types of Iraq War casualties vary greatly. Estimating war-related deaths poses many challenges. Experts distinguish between population-based studies, which extrapolate from random samples of the population, and body counts, which tally reported deaths and likely significantly underestimate casualties. Population-based studies produce estimates of the number of Iraq War casualties ranging from 151,000 violent deaths as of June 2006 (per the Iraq Family Health Survey) to 1,033,000 excess deaths (per the 2007 Opinion Research Business (ORB) survey). Other survey-based studies covering different time-spans find 461,000 total deaths (over 60% of them violent) as of June 2011 (per PLOS Medicine 2013), and 655,000 total deaths (over 90% of them violent) as of June 2006 (per the 2006 Lancet study). Body counts counted at least 110,600 violent deaths as of April 2009 (Associated Press). The Iraq Body Count project documents 186,901 – 210,296 violent civilian deaths in their table. All estimates of Iraq War casualties are disputed. The tables below summarize reports on Iraqi casualty figures. Scientific surveys: Body counts: Overview: Iraqi death estimates by source Summary of casualties of the Iraq War. Possible estimates on the number of people killed in the invasion and occupation of Iraq vary widely, and are highly disputed. Estimates of casualties below include both the 2003 invasion of Iraq and the following Post-invasion Iraq, 2003–present. Overview: Death estimates by group Overview: Iraqi injury estimates by source Iraqis: Deadliest single insurgent bombings: August 14, 2007. Truck bombs – 2007 Yazidi communities bombings (in northwestern Iraq): 796 killed. Other deadly days: November 23, 2006, (281 killed) and April 18, 2007, (233 killed): "4 bombings in Baghdad kill at least 183. ...