Yes it is possible the claim as currently defined could get the year of peak oil wrong. My reading of current rules is that judge would have to judge peak had occurred if such percentage changes happened again.
We are now further into oil production so another such large drop while still on the way up seems less likely. Also, there has to be some balance reached between how long to wait for judgement and how certain you want to be. The more likely concerning scenario to me is drops of between 0% and 1% such that we have to wait for around 10 years of data after the peak for it to be declared. To me this is rather long so rather than wanting to increase the 5% to make it more certain, I am wondering if we should make it easier to judge the claim earlier (even if it increases risk of judging it correctly per wording but wrongly as to actual peak oil date).
Perhaps (either 5% decline from peak level or 5 consecutive years of declines in total exceeding 2%) provided that there are widespread expectations of further declines in production? Hopefully, this attempts to make it more certain and can allow less waiting after peak in some circumstances?
If people wish to suggest whether we need to make it more certain or whether possibly waiting time after peak is more important, please do so. Suggestions on how to word it to get the best combination of both aims are also welcome.
Is a 5% drop enough? Based on that definition we reached peak oil in 1980. Of course production recovered subsequently but there were six years following 1980 where production was over 5% below 1980 levels, and two years when it was over 10% below 1980.