Nine times out of ten
Definition 1 of 1
Pro Tip 1/3Probability
The phrase suggests something happens 90% of the time but is not a precise statistic. 
If you check his blog, nine times out of ten, there's a new post.
Pro Tip 2/3Predictability
It indicates a high degree of certainty that an event will occur based on past occurrences. 
Nine times out of ten, she answers the phone on the first ring.
Pro Tip 3/3Casual Tone
The expression is informal, best for casual conversations, not for formal or academic writing. 
Nine times out of ten, going by bus is cheaper than taking a taxi.