Which factor primarily contributes to public debt?

The primary factor contributing to public debt is when government expenditures exceed its revenues. This situation occurs when a government spends more money than it collects through taxes and other income streams. To cover the shortfall, the government borrows money, often by issuing bonds. Over time, repeated deficits can lead to a significant accumulation of public debt.

In contrast, high rates of personal savings among citizens generally lead to increased capital available for investment and can encourage economic growth, rather than contributing directly to public debt. Increased taxation on corporations might actually help reduce debt by increasing government revenues, while investments in infrastructure, though potentially requiring funding, can also stimulate economic growth and increase future revenues. Hence, the correct choice highlights the fundamental imbalance between a government's income and its spending as the main driver of public debt.