Question about intercalation and publicationsWatch
And would the paper be peer reviewed or non?
There is also just a huge amount of luck involved, especially in lab projects. You can slave away for 6 months get all negative results and have nothing, or you can work for a week get a positive result and have a first author publication in a prestigious journal (as happened to a friend of mine).
Also people who do get publications are more likely to talk about it so just a vague impression is likely to be an overestimate.
My guess would be a third to half? Higher for a poster at a conference? Really just guessing though.