The Maritime Action Plan Needs a Yardstick: Enter the Mahan Ratio

Key Takeaways

• Mahan ratio = merchant fleet ships ÷ naval warships
• U.S. ratio 0.64 in 2025; China 20.31
• Plan proposes 1.0 ratio by 2035, 3.0 by 2045
• Tie Trust Fund disbursements to ratio milestones for accountability

Pulse Analysis

The Maritime Action Plan represents the most ambitious post‑World War II effort to rebuild America’s merchant marine, yet without a metric it risks becoming another line item on the budget. The Mahan ratio, a simple division of merchant vessels by naval warships, offers a historic yet underused gauge of sea power. By quantifying the commercial foundation that sustains naval operations, the ratio translates abstract policy goals into a tangible benchmark that can be tracked over time.

Recent data underscore why the metric matters. In 2025 the United States fielded just 188 U.S.-flagged merchant ships against 293 active naval vessels, yielding a ratio of 0.64—far below the 3.0 threshold that historically ensured logistical resilience in conflicts such as the Korean War. By contrast, China’s fleet composition produces a ratio above 20, reflecting a deliberate strategy that couples shipbuilding capacity with naval expansion. This disparity signals a strategic vulnerability for the United States: a shrinking commercial fleet limits sealift options, forces reliance on foreign‑flagged vessels, and erodes the economic leverage that underpins global maritime influence.

Embedding the Mahan ratio into the Maritime Action Plan could reshape funding and accountability. Setting a 1.0 ratio target by 2035 and a 3.0 target by 2045 would drive a phased increase in U.S.-flagged ships, while automatic budget triggers would compel the Maritime Security Trust Fund to scale up shipyard incentives when milestones slip. Including unmanned surface and subsurface platforms in the calculation acknowledges emerging technologies and ensures the metric stays relevant. With a clear yardstick, policymakers can evaluate progress, adjust investments, and ultimately restore the balanced maritime power that has historically secured America’s economic and strategic interests.