The U.S. dollar index®  is a measurement of the dollar's value relative to a basket of six different foreign currencies, as measured by their exchange rates. Over half of the index's value is represented by the dollar's value measured against the euro. The other five currencies consist of the Japanese yen, the British pound, the Canadian dollar, the Swedish krona, and the Swiss franc. 

The Index Formula

The dollar index is calculated using the following formula of currency pairs:

USDX = 50.14348112 × EURUSD ^-0.576 × USDJPY ^0.136 × GBPUSD ^-0.119 × USDCAD ^0.091 × USDSEK ^0.042 × USDCHF ^0.036

The value of each currency is multiplied by its weight. Note that the weight is a positive number when the U.S. dollar is the base currency, and negative when the U.S. dollar is the quote currency. Euros and pounds are the only two where the U.S. dollar is the base currency. That's because they are quoted in terms of the dollar. For example, a euro is worth $1.13. The other four are quoted in terms of how many a U.S. dollar will buy. For example, a dollar is worth 109 yen. 

History

In 1973, the Federal Reserve created the index to keep track of the dollar's value. It was right after President Nixon abandoned the gold standard that year, which allowed the value of the dollar to float freely in the world's foreign exchange markets. Before the creation of the dollar index, the dollar was fixed at $35/ounce of gold and had been that way since the 1944 Bretton Woods Agreement.

The dollar index began at 100. The index has measured the percent change in the dollar's value since the establishment of its base value. It changes constantly in reaction to shifts in the ongoing forex trades.

For example, its all-time high was 163.83 on March 5, 1985. That meant the dollar was 63.83 percent higher than in 1973.

Its all-time low was 71.58 on April 22, 2008. That meant it was 28.42 percent lower than its inception. 

In 1985, the ICE Futures U.S. took over the management of the USDX. That's the year that futures trading on the USDX began. 

Historical Data

Here is U.S. dollar index® historical data, as measured by the DXY, for the last 10 years.

2007: The dollar's value, as measured by the DXY spot price,  was 76.70 on December 31.

2008: The dollar ended the year at 82.15 after falling to a low of 71.30 on March 17, 2008. That was shortly after the Bear Stearns bailout signaled damage from the subprime mortgage crisis. At that time, investors thought it only affected the United States, and bought euros. The Fed lowered the fed funds rate 8 times. It initiated quantitative easing on November 25. By the end of the year, it was clear the 2008 financial crisis was worldwide. Investors returned to the dollar as a safe haven.

2009: The DXY ended the year at 77.92. The European Central Bank lowered rates, signaling it was responding to the crisis. The dollar fell as investors confidence in the euro rose. 

2010: The DXY rose to 88.26 on June 4, marking its high for the year. It fell to 78.96 by the year's end despite the Fed's launch of QE 2 on November 3.

2011: On May 2, the DXY fell to 73.10 due to the U.S. debt crisis. Investors returned to the dollar after the eurozone crisis. The Fed launched Operation Twist in September. The DXY ended the year at 80.21.

2012: The Fed announced QE3 on September 13 and QE4 in December. The DXY closed at 79.77.

2013: On June 19, the Fed announced it would taper off QE purchases. Investors sold bonds in a panic, driving the yield on the 10-year Treasury note up 1 percent. The Fed delayed tapering until December. The DXY closed the year at 80.04. 

2014: The dollar remained stable for the first six months, hitting 80.12 on July 10. The Ukraine crisis and Greek debt crisis drove investors out of the euro and into the dollar as a safe haven. The Fed ended QE in October. It held an unprecedented $4.5 trillion in Treasury notes.

 It announced it would raise the fed funds rate in 2015. By December 29, the dollar had risen 15 percent to 91.92.

2015: The European Central Bank announced it would begin QE in March. The euro fell to $1.0524 on March 12. The USDX hit the year's high of 100.18 on March 16, 2015. The dollar strengthened 25 percent from its 2014 low. On December 17, the Fed raised its benchmark rate to 0.5 percent. On December 27, the dollar ended the year at 98.69.

2016: On April 29, the dollar fell to its 2016 low of 93.08. On December 14, the Fed raised the fed funds rate to 0.75 percent. On December 11, it ended the year at 102.95. Since July 2014, it had risen 28 percent.

2017: Europe's economy improved, strengthening the euro. Hedge funds began shorting the dollar. The Fed raised rates on March 15, June 14, and December 13. On July 20, the European Central Bank signaled it might end QE in the fall. The dollar fell to 91.35, its low for that year, on September 8, 2017.  It ended the year at 92.12. 

2018: Early in the year, the dollar continued its decline. On February 15, the DXY fell to its low for the year of 88.59. That's down 14 percent from its 2016 high.  Investors were paring back their dollar investments as Europe's economy continued to strengthen. But then the U.S. economy improved while others' faltered. On November 12, the dollar index hit it 2018 high of 97.54. It ended the year at 96.17.

Historical Chart 

Year (last business day)	DXY Close	Factors Driving Dollar's Value
1967	121.79	Gold standard kept dollar at $35/oz.
1968	121.96
1969	121.74	Dollar hit 123.82 on 9/30.
1970	120.64	Recession.
1971	111.21	Wage-price controls.
1972	110.14	Stagflation.
1973	102.39	Gold standard ended. Index created in March.
1974	97.29	Watergate.
1975	103.51	Recession ended.
1976	104.56	Fed lowered rate.
1977	96.44
1978	86.50	Fed raised rate to 20 percent to stop inflation.
1979	85.82
1980	90.39	Recession.
1981	104.69	Reagan tax cut.
1982	117.91	Recession ended.
1983	131.79	Tax hike. Increased defense.
1984	151.47
1985	123.55	Record of 163.83 on March 5.
1986	104.24	Tax cut.
1987	85.66	Black Monday.
1988	92.29	Fed raised rates.
1989	93.93	S&L Crisis.
1990	83.89	Recession.
1991	84.69	Recession.
1992	93.87	NAFTA approved.
1993	97.63	Balanced Budget Act.
1994	88.69
1995	84.83	Fed raised rate.
1996	87.86	Welfare reform.
1997	99.57	LTCM crisis.
1998	93.95	Glass-Steagall repealed.
1999	101.42	Y2K scare.
2000	109.13	Tech bubble burst.
2001	117.21	Dollar rose to 118.54 on 12/24 after 9/11 attacks.
2002	102.26	Euro launched as a hard currency at $.90.
2003	87.38	Iraq War. JGTRRA.
2004	81.00
2005	90.96	War on Terror doubled debt. It weakened the dollar.
2006	83.43
2007	76.70	Euro rose to $1.47.
2008	82.15	Record low of 71.30 on 3/17.
2009	77.92	ECB lowered rates.
2010	78.96	QE2.
2011	80.21	Operation Twist. Debt crisis.
2012	79.77	QE3 and QE4. Fiscal cliff.
2013	80.04	Taper tantrum. Government shutdown. Debt crisis.
2014	90.28	Ukraine crisis. Greek debt crisis.
2015	98.69	Fed raised rates.
2016	102.21
2017	92.12	EU strengthened.
2018	96.17	Dow falls.

(Sources: "DXY Interactive Chart," Marketwatch. A higher number indicates a stronger dollar. For data earlier than 2007: sourced  DX.F from Stooq.com.  It is a futures indicator that gives an idea of where the dollar stood compared to its history.

In Depth: Value of Money | Dollar Versus Other Currencies | Today's Dollar Value