Original Sin and Currency Mismatch

A US company issuing 30-year bonds in dollars to fund a dollar-earning business faces no currency risk on its debt at all — it earns dollars, it owes dollars, the two match. Many emerging-market governments and companies don't have that luxury. Global investors are often unwilling to lend them money for the long term in their own currency, because they don't trust that currency to hold its value over decades, so the only way to borrow long-term in real size is to borrow in dollars, euros, or yen instead. Economists Barry Eichengreen and Ricardo Hausmann named this inability to borrow abroad in your own currency original sin — not a policy mistake a country made, but a structural condition it's often born into, tied to the depth and credibility of its own financial system.

Where the mismatch actually bites

Borrowing in dollars solves the immediate problem — the debt gets issued, the money arrives — but it creates a new one: currency mismatch. A government that borrows dollars but collects tax revenue in its own local currency, or a company that borrows dollars but sells its output for local currency, now owes a debt whose size in local-currency terms depends entirely on the exchange rate. That mismatch sits dormant and invisible as long as the currency is stable. It becomes the whole story the moment the currency moves.

Currency of debt	Currency of income	What happens if the local currency devalues 30%
Local currency	Local currency	Debt burden in local-currency terms is unchanged
Dollars (hard currency)	Local currency	Debt burden in local-currency terms rises roughly 43% relative to income, with no change in the dollar amount owed
Dollars (hard currency)	Dollars (e.g. an exporter)	Debt burden in local-currency terms unchanged relative to income — no mismatch

The devaluation math is the crux of it: if a currency falls 30% against the dollar, it takes about 43% more local currency to buy the same dollar (since 1/(1-0.30) ≈ 1.43), so a dollar debt doesn't just get "a bit more expensive" in local terms — it gets meaningfully more expensive precisely when the country is already under stress, because currencies rarely devalue during good times.

A worked scenario: a corporate borrower caught by the mismatch

A mid-sized manufacturer in an emerging market borrows $500 million via a dollar-denominated bond to build a new domestic factory, because dollar bond markets offered a far lower interest rate than borrowing in local currency was available for at that maturity. The factory sells almost entirely to the domestic market, invoicing customers in local currency — a completely ordinary, sensible-looking financing decision at the time it was made, and one thousands of EM companies have made for the same reason.

Two years later, a regional shock — say, a sharp commodity price move that hits the country's terms of trade — triggers capital outflows and the local currency falls 35% against the dollar over several months. The manufacturer's revenue, still collected in local currency, hasn't changed in real terms. But its $500 million of debt, translated back into local currency to compare against that revenue, now requires roughly 54% more local currency to service than it did before the devaluation. Interest payments that consumed a manageable share of operating cash flow now consume much more, covenant ratios calculated in local-currency terms deteriorate, and the company — which never took on any operational risk it didn't understand — finds itself in financial distress purely from an exchange-rate move it had no way to hedge cheaply, because long-dated FX hedges in that currency were themselves scarce and expensive for the same underlying reason the company borrowed in dollars in the first place.

Original sin has eased somewhat since the term was coined — some large emerging markets, including several with deep local bond markets, have built the ability to borrow long-term at home — but it remains the default condition for most smaller and lower-income economies, which is why so much of emerging-market analysis still starts with a simple question: what currency is this debt actually in, and what currency pays it back?