Lessee, .08 x 2.5*=0.2, so around 80% don't lie - sounds about right.
*In my experience, the 2.5x rule to apply to an initial estimate seems to be something of a universal constant; for example every place I've ever worked would announce a product introduction, but it would never really take place until the original schedule was twice as long and then rounded up to the nearest upcoming trade show. Similarly, everything I've done seems to take at least around 2.5 times as long as I think it will.
And everybody's familiar with the 80/20 rule.