There is no definitive argument for why I chose 10% opposition to an idea to indicate a lack of consensus. However, let me explain some of the reasoning I went through to choose that number.
- Consensus is not majority rule. If it was based on the majority, then there would always be a consensus on every issue, even if the percentage of qualified experts that advocated for a position was only 51%. I believe everyone will agree that if there if 49% of experts disagree with the majority position, then there is no consensus on this issue. However, once this point is accepted, the question becomes where to draw the line between competing viewpoints and a consensus on a particular topic.
- It should be relatively difficult to achieve a consensus. I would imagine most people would choose a number between 10 and 30 percent to establish a consensus. I have chosen the lower end of this spectrum because I think having a consensus should carry a lot of weight.
- When there is less than 5% opposition to a position, this is known as a ‘strong consensus.’ Both of the first two points could be used to argue for a consensus point at greater than 95% acceptance of an idea by qualified experts. I find it helpful to make a distinction between a consensus and near unanimity. I don’t believe this waters down the strength of a consensus. It just creates a category for things where there almost is no dissent at all.
I think it a good idea for those experts opposed to the consensus to not spread their views to the ignorant public, but to take it up with their colleagues why they disagree with the prevailing opinion. However, when no consensus exists, I see no need for this restriction.