The essential concepts for understanding public finance.

May 2026 by Javier García Díaz

This document addresses the fundamental concepts of public finance and the key indicators that allow for the assessment of the budgetary health and economic sustainability of the State. Analyzing the primary balance, the budget deficit, public debt, and the debt-to-GDP ratio provides a clear view of the balance of public accounts and its impact on investor confidence and the country's financing capacity.

Primary balance 

 The primary balance corresponds to difference between the revenue and expenditure of the State in its day-to-day operations, excluding interest charges on public debt. When this balance is negative, it means that revenues are not sufficient to cover primary expenses, which necessitates a review of fiscal policy. This indicator is particularly relevant for evaluating the Short-term budgetary discipline and the State's ability to finance its operations without depending on the cost of accumulated debt..

Budget deficit and public debt

The budget deficit is a broader concept that compares total government revenue with total government expenditure, including interest associated with public debt. Even if the primary balance is positive, the budget deficit may remain negative if interest charges are high. Internationally, this indicator is used to assess the sustainability of public finances and compliance with budgetary rules, reflecting the real need for additional funding by the State.

Public debt corresponds to the total amount that the State owes to its creditors, accumulated over time, and includes loans taken out and their respective interest. Although it is an essential instrument for financing public policies and responding to economic needs, it entails significant costs. The main difference between these two concepts lies in the time horizon: The primary balance reflects the short-term financial situation, while public debt results from decisions accumulated over the years. Nevertheless, they are directly linked: Successive deficits tend to increase debt, while greater control of public finances helps to curb its growth. Furthermore, higher interest rates increase the cost of debt, exacerbating its burden.

High levels of deficit or debt can affect investor confidence and the country's credibility, increasing economic risks. Furthermore, interest payments can limit investment capacity in essential areas such as health, education, or infrastructure, making balanced management of public finances essential.

Debt ratio as a percentage of GDP  

The percentage of public debt in relation to GDP — the debt-to-GDP ratio — measures the weight of accumulated debt relative to the productive capacity of the economy. This indicator compares the total value of public debt with the wealth generated by the country in a given year, allowing for an assessment of its sustainability. A high ratio indicates that debt represents a significant burden on the economy, potentially increasing the perception of risk among investors and influencing the cost of government financing. It is one of the main indicators used by financial institutions, rating agencies, and international organizations to assess the robustness of public finances.

Although distinct, these concepts are deeply related. The primary balance reflects the current state of public finances, the budget deficit reflects the overall balance, and public debt results from the cumulative effect of past decisions. Successive deficits tend to increase debt, while prudent fiscal management helps to stabilize its growth. On the other hand, higher interest rates increase the cost of debt, worsening the deficit and reinforcing the need for fiscal discipline.

High levels of deficit or debt can affect investor confidence and the country's credibility, directly impacting financing costs and the ability to respond to economic shocks. A balanced management of public finances is therefore crucial to ensuring macroeconomic stability and long-term sustainability.