In conclusion I guess it depends on your timescale. Trade for a few minutes / hours / possibly days, and you can just observe the market itself. But any longer, and you need to understand the fundamentals. For example, in US crude oil (WTI), the biggest news each week is 10:30 on Wednesdays (very exactly), when we get the US storage report listing the different oil products and how much of each product is stored in the US. The change from the previous week is the best read for the supply-demand condition. The data released is listed here:
http://ir.eia.gov/wpsr/wpsr.txtwith historical stats here:
http://tonto.eia.doe.gov/dnav/pet/pet_s ... s_w.htmYou have to know which number to read (mainly, the line called (9)), and preferably you have a few year's history because inventory has a seasonal pattern so a 'rise' in inventroy might be considered a 'fall' if a much larger rise was expected based on the time of year.If you don't know about this kind of thing, and you have an open position at 10:29:55 on Wednesday, the spot price of oil can move $2 in 10 seconds, more than the rest of the day put together, and your arb-trade is totally knocked out!