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The biggest influencer by far in my opinion is the site's marketing - whether the marketing is bringing in highly qualified and appropriate visitors or not. T
The other big influencer (again just my opinion & experience) is what's on the landing page. If the landing page gives the visitor enough info, there will be more bounce. If the landing page isn't helpful and people have to click just to find out what the site is really about, you'll have low bounce.
I've looked at bounce rates for many sites over the years and it varies from 90% down to 10% and is not a statistic I pay much attention to except for "same site, over time" kinds of comparisons.