The world's two largest stock exchanges, New York and Tokyo, formed an alliance recently to jointly develop financial products, including mutual funds and technology stocks and even discussed merging the two massive markets in the future.

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The alliance between the world's and Asia's largest exchanges, following a merger between the New York Stock Exchange and Euronext in June, casts further light on an increasingly visible trend: the world is becoming a single big investment platform.

With that as a backdrop, Hong Kong's exchange should look for partners to prevent being marginalized.

The best partner for Asia's second-largest exchange is definitely the mainland, because the two share much common ground.

They host a large number of same Chinese companies. And many of them are market movers that are increasingly global in influence, such as China Mobile and Sinopec. Investors in both regions have been analyzing each other's markets since the late 1990s, so they are well versed with one another.

There are signs that the two markets are already moving closer. A slump in Shanghai could drag down the performance of H shares in Hong Kong, while good news from Hong Kong can push up a stock's price in Shanghai in just a few minutes.

An important breakthrough came last year when the Industrial and Commercial Bank of China launched a precedent-setting simultaneous dual listing.

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