Financial markets are driven by numbers, but emotion plays a big role too.
There was plenty of emotion involved last week, as Wall Street had its worst one-day fall since 2011.
The Dow Jones Industrial Average fell more than 500 points, or 3 percent.
The sell-off was sparked by new fears about the global economy.
The latest manufacturing data from China suggests its economy is slowing faster than expected. Investors' nerves were not helped when oil briefly fell below US$40 a barrel.
The New Zealand share market starts trading at 10am, but the real focus of investors will be on what happens when the Asian markets start trading.
Watch the video for the full report from Tony Field.