But now they do that every day. The reason is simple: An active, bullish Shanghai market is gradually playing a bigger role in deciding the price of companies that list both in Hong Kong and Shanghai.

And at times, Shanghai even takes the lead.

Earlier this year a number of companies, such as China Eastern Airlines, Beijing North Star and China Life, saw sharp price surges in Hong Kong after their Shanghai-traded stocks gained.

This situation has prompted analysts to wonder which market will provide a fairer reflection of a stock's valuation in the future?

The issue appears to be all the more significant with a growing number of giants, previously only listed in Hong Kong, floating shares on the yuan-denominated Shanghai market.

They even include blue chips Bank of China and Sinopec that could influence the trend of Hong Kong's benchmark Hang Seng Index.

It is reasonable for Hong Kong to follow Shanghai. After all, the home market always knows better when it comes to its home companies. This is especially true when mainland investors more closely watch a market that has been on a bull run recently after a five-year lull.

But in an international context, Hong Kong will continue to provide the anchor price for a couple of years.

In valuing a company, Hong Kong investors look to their international peers and global market movements for hints.

The differing investor structure in Hong Kong and the mainland makes Hong Kong's price more rational.

Hong Kong is dominated by institutional investors with better knowledge and a global outlook, while Shanghai's market is dominated by individual investors known for their irrational decisions.