(Reuters) – Japan has stepped up its cautionary statements against sharp drops in the yen. In a rare joint statement, the government and central bank expressed “concern” about the actions. Investors are now wary of the possibility for intervention.

Japan has been intervening in foreign exchange markets more than a decade ago, and it’s more than 20 years since Japan supported its currency.

The Bank of Japan has provided a chronology of certain moves made in FX markets.

(Graphic on, Japan’s history of yen interventions: https://fingfx.thomsonreuters.com/gfx/mkt/xmpjoykbovr/Pasted%20image%201650518854154.png)

1973 – The Japanese monetary authority decides to allow the yen free movement against the greenback.

1985 – In the Plaza Accord, five industrial countries, which were the precursor to the G7 sign that the dollar has been overvalued, and they promise to reduce it.

1987 – Six G7 nations sign Louvre Accord on February 12, which aims at stabilizing currencies and halting the broad decline of the dollar.

1988 – The dollar drops to 120.45 Japanese yen in Tokyo Trade on Jan. 4. Bank of Japan intervenes, buying dollars and selling yen.

1991-1992 – Bank of Japan intervenes for the support of yen and sells U.S. dollar.

1993 – Bank of Japan purchases yen throughout the year in an effort to reduce its strength.

Between April 1994 and August 1995, the Dollar fell to an all-time low against both the German mark (and the Japanese yen) of a record. To support the greenback, the United States often intervenes with Japanese central banks and European central bankers.

1997-1998: The Asian financial crisis causes the yen to fall to almost 148 against the dollar in August. This is even though the Bank of Japan has been joined by the U.S. to purchase yen.

From January 1999 through April 2000, the Bank of Japan sold yen 18 times. This was due to concerns that a weak yen would impede an economic recovery. The Yen is still strengthening.

Sept. 2001 – The Bank of Japan intervenes and sells yen in response to the September 11th attacks in America. Both the ECB (New York Federal Reserve) and the ECB operate for BOJ.

May-June 2002 – Bank of Japan intervenes and sells yen. This is supported often by the Federal Reserve or ECB. The yen keeps on growing.

March 2004, the end of 15 months of campaign to reduce yen rise. Japan has spent a total 35 trillion yen (or more than $300 billion) on intervention.

September 15, 2010: Japan sells yen and intervenes on the currency market after the dollar hit a fifteen-year low at 82.87yen.

March 18, 2011: The G7 countries intervene jointly to stop yen volatility after it spikes to record levels in the wake of an earthquake. There was speculation that Japanese firms might repatriate assets abroad to finance reconstruction.

Aug. and Oct. 2011 – Japan intervenes as a stopgap measure to reduce gains, officials worry that they could derail the recovery from the economic slump caused by March’s earthquake and tsunami.