Equivalencies vary person to person and also depend on what you're considering 'equal'. Xanax has a much shorter half-life than Klonopin does, so it will accumulate to a much smaller degree given the same dose taken daily for a period of weeks.
Ashton's work indicates that someone on 4mg of Xanax a day should crossover to the same dose of Valium as someone on 4mg of Klonopin a day. That's what her equivalencies are based on. It may be that if you're taking a single dose to treat an acute condition, the numbers would change. Likewise, if you're considering long term use of one vs the other, the numbers may change in the other direction. It may also be that Klonopin is more sedating, so if the primary reason the drug was being taken was to create sleepiness, then a smaller relative dose of Klonopin would be appropriate relative to Xanax.
This is a fairly complicated issue, and because one of the variables is individual metabolism, there is no right or wrong answer. I think it's fair to say that "1mg of Xanax is the equivalent of 0.5mg to 2mg of Klonopin", because depending on the context it's possible to defend any combination of the math.