Institutional investors in Tokyo’s cosmopolitan Otemachi financial district are these days showing as much interest in the pronouncements of central bankers in Frankfurt and New York as in the utterances from the nearby Bank of Japan (BoJ) — and possibly even more.

While investors around the western world wait with bated breath to see if the U.S. Federal Reserve and European Central Bank are prepared to keep bolstering their economies with massive asset purchases or refinancing operations, the BoJ’s revelation that it was buying trillions of yen of extra assets failed on Friday to prevent a further fall in the stock market.

Traders’ underwhelmed response to the BoJ’s move confirms how the course of Japanese markets is being governed more by events elsewhere — particularly in the euro zone — than by the increasingly impotent central bank.

This was underlined by economists’ nervous reaction to Friday’s disappointing numbers for Japan’s export-focused manufacturing sector — an unusually key part of the economy for Japan since underlying long-term growth in domestic demand is low. Government data showed that manufacturers planned to cut production by 4.1 percent in May, and April’s survey of manufacturing purchasing managers by Markit Economics showed a fall in export orders. “Tokyo woke up to a rather chilly rain this morning, and the set of data released this morning was no better,” said Takuji Okubo, Asia chief economist at Société Générale in Tokyo. “Judging by manufacturers’ production plans, they do not seem to have much hope for rising export demand.”

To export successfully, Japanese manufacturers — which dominate the country’s Nikkei 225 stock index — need a weak yen. This makes their prices more competitive abroad as well as improves their earnings by increasing the value of their profits repatriated from overseas.

The yen fell sharply in the weeks after the BoJ’s Valentine’s Day declaration that it would pump more money into the economy by stepping up its asset purchasing in an effort to meet a new inflation goal of 1 percent. Such monetary easing should, in theory, create inflation by reducing the value of the yen, since an increase in the quantity of a currency cuts its value. A weaker currency increases inflation by raising the price of imported goods. The sharp depreciation in the yen sent the Nikkei 225, which is dominated by exporters, to a two-year high of 10,255.