Every HSC Economics Formula You Need to Memorise

NESA-approved calculators are permitted in the HSC Economics exam. There is no formula sheet. You carry every one of these in with you.

Expect two to four calculation or data-interpretation questions in Section I, plus calculations appearing in Section II, where the 2023 paper asked students to work out secondary income in the balance of payments.

Each formula below comes with a worked example using real Australian figures and, more usefully, the distractor: the wrong answer NESA includes because it is what the standard mistake produces.

---

Labour market

Labour force = employed + unemployed

Unemployment rate = (unemployed ÷ labour force) × 100

Participation rate = (labour force ÷ working-age population) × 100

Underemployment rate = (underemployed ÷ labour force) × 100

Underutilisation rate = unemployment rate + underemployment rate

Take a working-age population of 22.0 million, a labour force of 14.74 million and 0.65 million unemployed. The unemployment rate is 0.65 ÷ 14.74 × 100 = 4.4%, and the participation rate is 14.74 ÷ 22.0 × 100 = 67.0%.

The distractor comes from dividing the unemployed by the working-age population instead of the labour force, giving 0.65 ÷ 22.0 = 3.0%. That number will be sitting among your four options. The unemployment rate uses the labour force as its denominator. The participation rate uses the working-age population.

This one matters more than the others because NESA's 2025 examiners specifically reported students blurring those two rates on the Section II question. It is the most reliably tested confusion in the whole course.

There is also a trap here that is not arithmetic at all. If discouraged workers leave the labour force, the unemployment rate can fall while employment is completely unchanged, because the denominator shrank. Questions get engineered around exactly that.

---

Prices and inflation

Inflation rate = ((CPI₂ − CPI₁) ÷ CPI₁) × 100

Real value = nominal value ÷ (CPI ÷ 100)

Real wage growth ≈ nominal wage growth − inflation rate

Wage Price Index growth was 3.3% over the year to the March quarter 2026, against headline inflation of 4.6%. So real wage growth was roughly 3.3 − 4.6 = −1.3%, and real wages fell.

The distractor here is comparing nominal wage growth against trimmed mean inflation, which was 3.3% in March 2026, instead of headline. That gives roughly zero and an entirely different conclusion, so read which measure the question actually hands you.

Keep the two measures straight. Headline CPI is the whole basket. Trimmed mean strips out the most volatile 30% of price movements to show the underlying trend. Since November 2025 the monthly CPI has been Australia's headline measure, with the quarterly series calculated as the average of the three monthly figures.

---

External sector

Terms of trade index = (export price index ÷ import price index) × 100

Current account = balance on goods and services
                + net primary income
                + net secondary income

Balance on goods and services = (exports − imports of goods)
                              + (exports − imports of services)

Current account + capital and financial account
                + net errors and omissions = 0

For the March quarter 2026, with a goods and services balance of −$2.4b, net primary income of −$23.7b and net secondary income of −$1.0b, the current account is −2.4 − 23.7 − 1.0 = −$27.1 billion.

The distractor is writing the identity as "current account + capital and financial account = 0" and solving for the capital and financial account. That omits net errors and omissions, and in any question giving you a small residual, the omission is precisely what the wrong option is built from.

Put the terms of trade in words as well as symbols. A rise means export prices climbing faster than import prices, so a given volume of exports buys more imports. That is an improvement, and it is what drove Australia's record current account surpluses in 2021.

---

National accounts and growth

GDP (expenditure) = C + I + G + (X − M)

Real GDP growth = ((real GDP₂ − real GDP₁) ÷ real GDP₁) × 100

Real GDP = nominal GDP ÷ (GDP deflator ÷ 100)

GDP per capita = real GDP ÷ population

Real GDP grew 0.3% in the March quarter 2026 and 2.5% through the year, while GDP per capita grew 1.0% through the year.

The gap between those last two figures is population growth, and it is worth deploying. Aggregate growth flattered by population is one of the most reliable evaluation points available in any question about whether growth has improved living standards.

---

The multiplier

Simple multiplier  k = 1 ÷ MPS = 1 ÷ (1 − MPC)

Change in income   ΔY = k × ΔExpenditure

MPC = change in consumption ÷ change in income
MPS = change in saving ÷ change in income          (MPC + MPS = 1)

With an MPC of 0.5, k = 1 ÷ (1 − 0.5) = 2, so a $25 billion increase in government spending raises equilibrium income by $50 billion.

The distractor is using 1 ÷ MPC. At an MPC of 0.5 that coincidentally gives the right answer of 2, which is how the error survives, but at an MPC of 0.8 it gives 1.25 when the real answer is 5. The denominator is the marginal propensity to save, not consume.

There is a free evaluation mark attached whenever you use this. The simple multiplier overstates the real effect, because leakages to taxation and imports are nowhere in the formula.

---

Fiscal policy

Budget outcome = receipts − outlays        (negative = deficit)

Budget outcome as % of GDP = (budget outcome ÷ nominal GDP) × 100

Debt-to-GDP ratio = (debt ÷ nominal GDP) × 100

The 2026-27 Budget forecasts an underlying cash deficit of $31.5 billion against nominal GDP of roughly $3.1 trillion, so 31.5 ÷ 3,091 × 100 gives approximately 1.0% of GDP.

Know the distinction between measures. The underlying cash balance excludes volatile one-offs such as Future Fund earnings, and it is both the headline figure quoted in the Budget papers and the one you should cite.

---

Distribution

Gini coefficient = area A ÷ (area A + area B)

A is the area between the line of perfect equality and the Lorenz curve, and B is the area beneath the curve. It runs from 0, meaning perfect equality, to 1, meaning one household holds all income.

You will not be asked to compute a Gini from raw data, but you do need to sketch and read a Lorenz curve. It was examined in Section II in 2023 and Section III in 2025.

---

The three habits that save these marks

Check the units before you compute anything. Tables mix $m and $b, levels and percentages, quarterly and annual, and NESA reliably includes a distractor that is the correct method applied to the wrong unit, giving an answer out by a factor of a thousand that looks entirely plausible on the page.

Predict the direction before you calculate. Decide whether the answer should rise or fall first, so that when your arithmetic contradicts your economics you know it is a keystroke error rather than a discovery.

Distinguish a level from a rate of change. A falling line on an inflation chart means prices are still rising, just more slowly, which is disinflation rather than deflation. That one catches strong students every single year.

---

How to drill them

Write the whole set out from memory once a week. It takes four minutes and it is the highest return per minute of any revision in the course, because unlike essay technique these are binary. You either have the formula or you do not.

Then do Section I from ten past papers under a 25-minute clock, logging every calculation error by type: wrong formula, wrong units, wrong direction, arithmetic slip. Most students discover the majority of their losses are units and direction rather than the formulas themselves.

There is more on that method in our guide to the multiple choice section, and the current figures to practise on are in the Australian economy statistics page.