Any thoughts as to why the preferred direction is down?
I can make up stories as to why – but that would just be for entertainment, because I really don't know.
Presumably, that particular direction enables the bankers to make money somehow. 🙂 Anyone going through the effort to predictably distort the market on a daily basis has to be doing it for a reason. Now, I don't know enough about the mechanics of how they can skim from hammering the price before the fix, so I can't answer the question you really are asking – what is their mechanism for cashing in on this move.
And likely it wasn't every day. Just some days. I certainly don't notice it happening every day. Why some and not others? Perhaps it was done to enhance profitability of (unknown) derivative positions that were based on the value of the fix on certain days. But again, I'm just guessing at the mechanics of how. The why I'm pretty certain of.
Even on average, though, this behavior was egregious enough so that even in the face of the overall gold market rising during the period [1-1-2007 through 1-28-2014, $639 to $1255], if you'd bought 15 minutes before the fix, and sold at the moment of the fix, you'd have lost $407 over the course of the entire gold bull market. Still – that's 1825 trading days, so you'd get poor at about 23 cents per day. Tough to make money shorting gold during that time period with a 10 cent spread on both ends.
This is actually true for both "fix" times – the AM fix at 0515-0530 EST, and the PM fix at 0945-1000 EST. "the worst 30 minutes of the day" for gold – both periods down -$400 over the course of the 8 year period I studied.
The two best periods of the day: immediately after the PM fix at 1000 EST ($282) and at the open in Asia at 1800 EST ($214).