What's behind the latest surge in the US dollar?

12 September 2018 | Markets and Economy


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 Commentary by Roger Aliaga-Díaz, Vanguard senior economist.

Over the last four years, the US dollar has appreciated sharply. We've seen the exchange rate between a basket of major developed markets currencies and the dollar shoot up more than 20% since July 2014. After a short break in 2017, the dollar resumed its brisk climb, rising more than 5% in the first five months of this year and triggering concerns among investors and economists about US dollar-related disruptions to the global economy and financial markets.

This seems like a good time to share a few observations about the behaviour of the US dollar and also to form a view – or at least an informed guess – about how things may go from here.

Keep in mind, however, that predicting the timing and magnitude of currency moves is challenging. Most currency models developed by economists cannot fully explain historical patterns, let alone produce forecasts that can systematically beat the consensus. So it's important to maintain healthy doses of humility and discipline in designing long-term investment plans based on any projections about the dollar.

Tracing the dollar's ups and downs

Let's start with a simple historical observation about the dollar: Since 1973, its value has remained in a relatively tight range compared with other major currencies, except for three multiyear "super-cycles."1 As you can see in the accompanying chart, we're in the midst of the third such super-cycle right now.

Three super-cycles in the US dollar since 1973

Source: Vanguard calculations using data from the US Board of Governors of the Federal Reserve System.

Notes: The US dollar index shows the trade-weighted average exchange value of the US dollar against a basket of currencies that includes the euro, the Japanese yen, the Canadian dollar, the British pound, the Swedish krona and the Swiss franc after adjusting for inflation. Data are from January 1973 through June 2018. The average "normal" valuation was calculated by excluding real dollar index readings above 90.

Different causes, similar outcomes

While the chart suggests a statistical regularity and reversion to the mean, each upswing in the dollar has had a different cause. The magnitude and duration of each upswing have varied as well.

The first big swing, from about 1979 through 1987, coincided closely with Paul Volcker's tenure as chairman of the Federal Reserve and his fight to bring inflation under control by raising the federal funds rate to 20% in 1981.

The second super-cycle ran from the mid-1990s through about 2004 as global capital poured into the United States, attracted by the bright earnings prospects for the new IT and dot-com companies. After the bubble burst, and capital inflows eased as US-developed technologies spread to companies worldwide, the markets and the dollar returned to more normal levels.

We're now in the midst of the third US dollar super-cycle. It started around July 2014, as the Federal Reserve led other major central banks in signalling the end of a period of extraordinarily loose monetary policy.

Because the US dollar is the world's reserve currency, these super-cycles can send shockwaves across the globe, affecting emerging markets in particular. The 1982 Latin American debt crisis, the 1997 currency crises in Asia and Latin America, and the multiple mini-emerging-markets crises we have seen since 2014 (in Brazil, South Africa, Argentina and Turkey among others) have all coincided with peak valuations for the US dollar.

However, while the dollar was at the centre of these meltdowns, in almost every instance the ultimate cause of the collapse was those countries' precarious macroeconomic fundamentals, brought about by dollar-debt-fuelled booms (and sometimes exacerbated by a central bank's pegging the country's currency to the dollar). The subsequent unwinding of these emerging markets booms can be fast and furious, but placing blame on the dollar alone misses the bigger picture.

The lesson from these super-cycles is that economic fundamentals drive currency movements. So while it's commonly believed that strength in the dollar causes weakness in the US economy, it actually seems to work the other way around: The strong US economy (relative to the rest of the world) and the Fed policy that goes along with strong fundamentals have been the primary drivers behind the dollar's appreciation.

If past is prologue, the dollar will weaken

We can therefore expect the dollar super-cycle to come to a close over the next few years. Here are four fundamental factors, not mutually exclusive, that I'll be watching for:

  1. Narrower growth differentials between the United States and other countries. The US economy is much further along in the business cycle than other developed markets, its labour market is much tighter, and inflation is much closer to the central bank's target, which in the United States is 2%. Since economic growth normally slows late in the cycle, current growth differentials between the United States and other economies are expected to shrink. The next slowdown in the United States may be exacerbated when the recent fiscal stimulus wears off. We estimate that the stimulus, injected through the tax cuts and spending bill enacted at the beginning of the year, will deliver an extra push to US economic growth of about 40 basis points this year and next.
  2. Higher US bond yields, but narrowing interest rate differentials. Higher bond yields in the United States today imply depreciation in the US dollar relative to other major currencies in the future. This market expectation may come to pass in the current global monetary cycle as the gap in rates between the US and other major markets narrows. The Fed may stop raising rates as soon as 2019 while other central banks (notably the European Central Bank and the Bank of England) continue to play catch-up.
  3. Higher inflation in the United States. Higher inflation in the United States relative to other developed markets could put downward pressure on the nominal US dollar exchange rate.
  4. A larger US trade deficit. For all the noise about tariffs and trade deficits, the natural way for trade imbalances to correct over time is through market-driven currency adjustments. Widening US trade deficits translate into higher demand for foreign currency (to pay for the additional imports), which exerts downward pressure on the dollar. The trade deficits themselves are caused in part by rising government budget shortfalls, which spill over to more foreign purchases of US debt. Trade deficits are also caused in part by strong US consumer spending, which, bolstered by tax cuts, results in more purchases of imported goods, given that they constitute about 18% of the typical consumer basket.

Dollar trends and investing

Dollar moves have significant implications and risks for almost every corner of the capital markets, from emerging markets equities and bonds, to broader global non-US equities (hedged or unhedged), to commodities.

It's important to keep in mind, however, that these dollar trends may play out over time frames that don't match an investor's needs. Market valuation measures, such as the fundamental factors discussed earlier, are not a good market-timing tool for those with shorter investment horizons. Market prices, whether for equities or currencies, can deviate from fundamentals for much longer than many think.

For investors more inclined to actively position their portfolios based on macroeconomic views, it's critical to discern which economic trends have already been factored into market prices and which constitute out-of-consensus economic calls. Only the latter will translate into outperformance relative to a benchmark if proven right (or underperformance if proven wrong).

Roger Aliaga-Díaz
Vanguard senior economist

1 Why 1973? That's when the dollar began to float freely after the United States ended its fixed parity with gold, which had been established by the Bretton Woods Agreement in 1944.

Investment risk information:

The value of investments, and the income from them, may fall or rise and investors may get back less than they invested. Past performance is not a reliable indicator of future results.

Other important information:

This article is directed at professional investors and should not be distributed to, or relied upon by, retail investors.

This article is designed only for use by, and is directed only at persons resident in, the UK. It is for educational purposes only.

This article was produced by The Vanguard Group, Inc. It is not a recommendation or solicitation to buy or sell investments.

The opinions expressed in this article are those of the individual author and may not be representative of Vanguard Asset Management, Limited.

Issued by Vanguard Asset Management, Limited which is authorised and regulated in the UK by the Financial Conduct Authority.


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