Allocated portfolio vs. Dow - I'm puzzled.

[mountainhouse]

I've been working my way through the Bernstein book. All makes great sense, until I look at how Vanguard 2020 tracks against the Dow. I'm surprised at how closely it tracks. If the 2020 fund represents diversification, I'd expect it wouldn't be this close.
^DJI: Basic Chart for DOW JONES INDUSTRIAL AVERAGE IN - Yahoo! Finance

[twaddle]

Target 2020 is 70% stock, and mostly large-cap just like the Dow, so I'd expect it to follow pretty closely.

International has been strongly correlated to US markets recently.

I like how they tossed 2% emerging market into the fund. I wonder how they determine these allocations.