Investment, the Multiplier, and Whether Investment Is a Key Determinant of Singapore's Macroeconomic Performance
Answer
Part (a)
The circular flow of income describes income flowing from firms to households as factor payments and back as consumption spending, raised by injections (investment, government expenditure, exports) and reduced by leakages (saving, taxes, imports). Investment — spending on capital stock, human capital and inbound FDI — is an injection that does not arise from current income.
Suppose investment rises by $100m. Injections now exceed leakages, so planned spending exceeds current output; firms’ stocks deplete, prompting them to raise output and hire more factors, paying out $100m in additional factor income — a first-round rise in national income. Households re-spend a fraction on domestic goods: with a marginal propensity to consume domestically of 0.6, they spend $60m, while $40m leaks into saving, taxes and imports. This $60m triggers another round of output and income, of which $36m is re-spent, and so on, each round smaller. The process continues until the induced rise in leakages equals the initial $100m injection. Summing the rounds, the total rise in national income is the injection times the multiplier , i.e. $250m — a bigger change in national income than the initial injection. The larger the multiplier (the smaller the marginal propensity to withdraw), the larger the final change.
Part (b)
Macroeconomic performance is judged by economic growth, price stability, employment and a healthy balance of trade, all driven by aggregate demand and aggregate supply. The thesis is that the level of investment is a key determinant — uniquely, it works on both AD and AS — but for a small, open Singapore it is not the only key determinant: net exports rival it in the short run, and the verdict turns on the time horizon.
Investment works on both AD and AS. Below full employment, a rise in investment raises AD via the multiplier (part a), raising real output and, through derived demand, employment — actual growth. As the economy nears capacity, further AD increases bid up scarce resources and generate demand-pull inflation. Crucially, investment also acts on the supply side: spending on better machinery, technology and skills raises productive capacity, shifting LRAS right — potential growth — which raises sustainable output and eases the price level in the long run. Investment is therefore a determinant of growth, employment, inflation and, by raising competitiveness, the balance of trade.
For Singapore specifically, a low 17% corporate tax and its standing as a major financial centre draw substantial FDI, which a small, resource-scarce economy depends on for funding, technology and access to global markets — so investment is genuinely important here.
But net exports rival it. Singapore’s total trade exceeds 300% of GDP and export revenue alone is around 176% of GDP, so a change in net exports moves AD far more than a change in the small domestic consumption base. MAS’s modest, gradual appreciation lowers imported input costs, containing cost-push inflation and sustaining export competitiveness and the balance of trade. Consumption, by contrast, is a relatively minor driver given the small domestic market, and technology/R&D mainly operates through investment in any case.
Judgement. Investment is a key determinant, but whether it is the key determinant depends on the horizon. In the short run, export revenue is plausibly the dominant influence on Singapore’s macroeconomic performance, since at ~176% of GDP a swing in exports affects AD far more than investment or consumption — as the COVID-19 collapse in external demand made vivid. In the long run, however, investment is the more important determinant: it is what raises productive capacity, and Singapore’s ageing population and recent fall in labour productivity make capacity-raising investment essential for sustainable growth — whereas export revenue is largely hostage to uncontrollable external conditions. The defensible stand is that investment is the key determinant of Singapore’s long-run macroeconomic performance through its dual effect on AD and AS, while net exports dominate in the short run.