There’s no overall theory of how world currencies interact with one another.  Rather, there’s  patchwork of general relationships.  I find two most useful:

—general creditworthiness, or would I lend money to these guys (WILMTTG)?.

Another way of asking the same question is whether a country can generate enough foreign exchange to pay for its imports and meet the minimum service requirements on its foreign borrowings.  A “No” answer means trouble.

Natural resources-oriented emerging countries, both in the Middle East and in Latin America, are going to flunk this test, suggesting that for them currency depreciation is in store.

—relative interest rates 

Generally speaking, countries where interest rates are rising will have stronger currencies than those where rates are stable or falling.

This rule suggests that the US$ will continue to rise against the euro, yen renminbi and emerging markets currencies–meaning just about everything.

 

As a practical matter, domestic stock markets seem to work best when a currency is stable or depreciating slightly.  A rising currency, because it lowers the domestic currency value of foreign earnings, acts as an earnings headwind.

 

I’ve found that the currency markets–read: traders in the big multinational commercial banks–are always three or four steps ahead of me in figuring out where currencies are going.  For equity investors, there may also be an issue of how the companies whose stocks they hold are acting internally to hedge their foreign currency exposure.

Typically, this second isn’t as big an issue as it might seem at first.  Stock markets most often understand that hedges now protecting profits will soon expire and, in consequence, pretty much ignore the earnings per share generated by hedging.

The question of what’s already baked in the currency trading cake is a more serious one.  It has me questioning whether any interest rate rises that may come in the US next year aren’t already factored into today’s currency rates.

my conclusions

The US$ will be flat to up vs. all other currencies next year.

The yen will be down, on my “No!” answer to the WILMTTG question.

Emerging market currencies will generally be weak.

The renminbi will be flattish, on weak relative rates but “Yes to WILMTTG.

Too soon to act on, but will the euro be stronger in the second half?

stock market implications

All other things being equal, companies with costs in weak currencies and revenues in strong currencies will have the best financial results.

Multinational companies based in the US with exposure to natural resources emerging markets may do poorly.

Those with EU exposure may show slim growth, if any, in their operations there in the first half.  Better news in the second?

As a general rule, when the domestic currency is rising, look for purely domestic companies and for importers.