I was taught while at university, that Chimps and Humans were only 1 to 1.8% different (results from the inference given in nucleotide hybridization were used), so I have always thought it was a 98 to 98.2% match. I wanted to make sure so I looked at years of notes including notes from 1992 and 93 after graduating and attending several lectures by the great Stephen J. Gould, Vince Sarich and Karl Sigmund. They all said 98 or higher. In fact I remember Sarich insisting upon a 99% match while debating some creationist clown just a few years ago.
Four percent difference is too large and is much more than it appears to me using observation with the naked eye. Some Chimps seem quite Human, much closer than the looters we witness in NOLA, and I think the findings are not the last word, it has to be closer.