SDI off topic chat., page-17

I have quickly scanned through this paper which asserts that overconfidence in men leads to inferior returns v women.

https://faculty.haas.berkeley.edu/odean/papers/gender/boyswillbeboys.pdf

I am not convinced.

The argument goes:

1) Men tend to be more overconfident than women - I can believe this
2) Men trade more than women - The link between overconfidence and trading regularly is not proven imo. For example, lack of confidence could lead to over trading as the trader is never confident enough to hold their existing positions for any length of time. Plus, the data is taken from women and men who have set up trading accounts. What about the vast majority of both women and men who never buy shares?
3) Trading regularly leads to inferior returns - this is "proven" by comparing actual performance to performance if portfolio positions at the start of the year are maintained for 1 year (ie no trading in that year). Well, 1 year is a bit arbitrary isn't it? What if two years or some other longer time period led to lower returns? Is it still fair to say that the more trading you do the worse your returns will be?