Wars also tend to have significant spillover effects. Countries engaged in foreign conflicts may avoid large economic losses—partly because there is no physical destruction on their own soil. Yet, neighboring economies or key trading partners with the country where the conflict is taking place will feel the shock. In the early years of a conflict, these countries often experience modest declines in output.
Major conflicts—those involving at least 1,000 battle-related deaths—force difficult trade-offs in economies where they occur. Government budgets deteriorate as spending shifts toward defense and debt increases, while output and tax collection collapse.
These countries may also face strains on their external balances. As imports contract sharply because of lower demand, exports decrease even more substantially, resulting in a temporary widening of the trade deficit. Heightened uncertainty triggers capital outflows, with both foreign direct investment and portfolio flows declining. This forces wartime governments to rely more heavily on aid and, in some cases, remittances from citizens abroad to finance trade deficits.
Despite these measures, conflicts contribute to sustained exchange rate depreciation, reserve losses, and rising inflation, underscoring how widening external imbalances amplify macroeconomic stress during wartime. Prices tend to increase at a pace higher than most of central banks’ inflation targets, prompting monetary authorities to raise interest rates.
Taken together, our findings show that major conflicts impose substantial economic costs and difficult trade-offs on economies that experience conflicts within their borders, as well as hurting other countries. And these costs extend well beyond short-term disruption, with enduring consequences for both economic potential and human well-being.
Spending trade-offs
More frequent conflicts and rising geopolitical tensions have also prompted many countries to reassess their security priorities and increase defense spending. Others plan to do so. This situation presents policymakers with a crucial question about trade-offs involved with such a boost to spending.
Our analysis looks at episodes of large buildups in defense spending in 164 countries since the Second World War. We find that these booms typically last nearly three years and increase defense spending by 2.7 percentage points of gross domestic product. That’s broadly similar to what is required by North Atlantic Treaty Organization (NATO) members to reach the 5 percent of GDP defense spending target by 2035.
Ramping up defense spending primarily acts as a positive demand shock, boosting private consumption and investment, especially in defense-related sectors. This can raise both economic output and prices in the short term, requiring close coordination with monetary policy to temper inflationary pressures.
Overall, the aggregate effects on output of scaling up defense spending are likely modest. Increases in defense spending typically translate almost one for one into higher economic output, rather than having a bigger multiplier effect on activity. That said, the multiplier or ripple effects of such spending vary widely depending on how outlays are sustained, financed and allocated, and how much equipment is imported.
For instance, output gains are smaller and external balances deteriorate when the stimulus is partly spent to import foreign goods, which is especially the case for arms importers. By contrast, a buildup of defense spending that prioritizes public investment in equipment and infrastructure, together with less fragmented procurement and more common standards, would expand market size, support economies of scale, strengthen industrial capacity, limit import leakages, and support long-term productivity growth.
The choice of how to finance defense spending entails critical trade-offs. Defense spending booms are mostly deficit-financed in the near-term, while higher revenues play a larger role in later years of defense spending booms and when the defense spending buildup is expected to be permanent.