It is not a question of argument, the rounded-down figure of six million is not disputed by academic historians. The point is that the figures of two-and-a-half million and six million do not clash, one is included in the other.
However, these numbers are about to be settled precisely once-and-for-all. In May 2006 international agreement was finally reached on opening the Nazi Archives. Go here
BBC NEWS | World | Europe | Nazi crimes archives set to open for details and for a video tour of the archive.