How to counter Jax
Let us take a look on how to beat Jax. We will look at champions who are strong against Jax and who are weak against Jax. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Top champion who counters Jax. You can already win in champion select with the right counters for Jax. If you want to know how to counter Jax then you need to take into account the best picks vs Jax and the worst picks vs Jax. This Jax counter data is based on matches played by Pros on patch 15.11 and previous ones. It is important to see whether Pros counter picked Jax or whether they played as Jax.
Champions used by Pros to counter pick Jax
Looking at the matches from Pros (see table Pros counter picked Jax) we can see that they picked 
Gwen most often to counter pick Jax. The matchup Gwen vs Jax occured 30 times. Jax has 21 wins and 9 losses in this matchup. Learn how to counter pick Gwen to get another perspective on the data.
Lane outcome for Jax
When looking at Jax counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Jax. The lane outcome of Jax consists of three outcomes: Win, Loss or Draw. Let's take a look of Jax lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Jax.
Conclusion
Analyze the available data and learn how to beat Jax. To master Jax take also a look on Jax builds and runes for Jax. Good luck, Summoner!