Basic statistics: just because the average in the top decile is 74, that doesn't mean everyone in the top decile drinks 74. The top 5%/1%/0.1% who drink way more than 74/week (15/day? 20/day?) can counter-balance the 5-8/day crowd.

To give another example: the average top decile Facebook employee has a net worth over $33 Million. That seems high, but that's because that net worth is highly skewed - in fact, I assumed only Mark Zuckerberg's wealth was distributed equally among FB's ~10k employees, and that everyone else has $0. The figure $33 Million is meaningless.