Some traders think only the US markets are worth trading. Some think only the EU markets are worth their time. I trade both markets, starting the day at 8:45 AM, and ending around 22PM. The reason this is important for me is the way these markets relate to each other. Usually, a strong intraday trend in Europe will result in a gap at the US opening, and a narrow intraday range later. A strong intraday trend in the US, and no news in the evening will also result in a gapping open in Europe, and probably a choppy day. Usually this relation is moderated, both markets showing small gaps and decent intraday trends. But, sometimes, the ability to trade both the US and EU matters... Example from the last 3 days : First number is the intraday range in percent. Second number is the change at the close in percent. The CAC40 is the broad French index (40 large caps, some of them having ADRs quoted on the NYSE) COMPX 1.83% 5.07% 1.98% -3.90% 1.57% 3.24% CAC40 5.76% 6.96% 1.71% -0.59% 2.95% 3.76% As one can see most profits on the US markets these late days have been on the gaps. And most of the profits on the EU markets have been made intraday. I did not trade the US after the 6.96% up day in the CAC, I was expecting some chop-chop after the big up gap. But this day was not wasted for me since I profited to the extreme from the intraday move in the CAC. To conclude : the ability to trade both markets almost guarantees a trader to be able to profit from an intraday trend everyday. So, for anyone serious enough in their trading, the dedication required to follow both markets can be more than worth it. OHLC
European markets often follow the US markets although they open ahead of us. The CAC 40 can be green the entire day until the NYSE opens. It then follows what Nasdaq and Dow are doing. I prefer to concentrate on only one market.