What has caused the sudden anxiety attack that overwhelmed financial markets after the New Year? We may find out the answer at 8.30 on Friday morning, Eastern Standard Time.

Almost all agree that the market turmoil has been linked to alarming events in several emerging economies — including Turkey, Thailand, Argentina and Ukraine — that has spilled over into concerns about more important economies, such as China, Russia, South Africa, Indonesia and Brazil.

But why has near-panic hit so many emerging markets at the same time?

There seem to be four broad explanations. Whether this current volatility marks the end of the straight-line ascent in asset prices that started in March 2009, or whether it is just another opportunity to “buy on dips,” will largely depend on the relative importance of each of these factors.

Most headlines about the emerging market instability blamed China — especially a plunge in Chinese economic statistics released New Year’s Day.

If China is really the main cause, investors can relax. Not because China’s weakness and credit tightening is an illusion, but because virtually every business and investor in the world has been aware of the Chinese slowdown for more than a year now. And so has Beijing.