What Made South Korea the Saddest Country in the OECD?

In my previous posting, I found South Korea's suicide death rates were the highest in the OECD.
I tried to figure out possible causes of the grim facts.
Among some seemingly suicide-related sad statistics, I found one statistically meaningful evidence.
It is the "wage dispersion" in the country. Wage dispersion is the ratio of the wages of the 10% best-paid workers to those of the 10% least-paid workers.
As you can see from the figure below, the wage dispersion has been increasing over the 15 years' span from 1994 to 2008.


It is highly correlated with South Korea's suicide rates. In a simple linear regression, the square of the correlation coefficient between the two variables was 0.8648.

Then, what is causing the ever-increasing wage dispersion in South Korea? I'll find the answer when I'm free of some duties.

Data sources:
Statistics Korea. (2011). Annual Report on the Cause of Death Statistics. [Data from http://j.mp/Cause_of_Death]

OECD. (2011). Divided We Stand: Why Inequality Keeps Rising. Paris, France: OECD Publishing. [Full-text from http://dx.doi.org/10.1787/9789264119536-en]