How can Gmail be this bad?

I've attached a screenshot from the top of my gmail account. How these spam emails, in in Cyrillic, Chinese, and Japanese (I think) made it through gmail's filters baffles me. Yahoo! mail has much better spam filters.



I'm also a surprised that anyone would bother with non-English spam. The response rate to English emails has to be better than Russian emails, so why bother with non-English spam at all?

Hypothesis:
1) English speakers are savvy about spam now, so although there are fewer Russian and Chinese internet users, they are still more gullible.

2) Gmail is smart about filtering out english spam, but dumb about Russian and Chinese spam. So Russian and Chinese spam is appropriately rare, I just see it more.

3) Russiand and Chinese spammers are still new at the game, and will switch to English once they gain experience.