The best performer this year among developed nations, New Zealand’s S&P/NZX 50 Index, has been a market darling, until now. The gauge is leading losses among major indexes as concern central banks are questioning loose monetary policy pummels risk appetite. The NZX’s so-called Z score, a measure of how many standard deviations away from zero, or the mean, the index has moved breached negative 4 for only the fifth time in more than eight years Monday, with three of those moves happening in the summer of 2011.

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