A balanced growth path (BGP) is a long-run growth trajectory where key aggregates (such as output (Y), capital (K), and consumption (C)) grow at constant rates and certain ratios remain stable (such as (K/Y)). It is a central benchmark in growth theory because it describes what “steady” growth looks like once transitional dynamics have played out.
Core Mechanics (Solow-Style Intuition)
In the Solow model with labor-augmenting technology (A) and labor (L), a common production function is:
[ Y = K^\alpha (AL)^{1-\alpha} ]
Define capital per effective worker as (k = K/(AL)). A steady state is a constant (k). When (k) is constant, (Y/(AL)) is constant too, and the economy is on a balanced growth path in which:
- (K), (Y), and (C) grow at the same rate,
- the long-run growth rate of (Y) is driven by population growth and technology growth, and
- ratios like (K/Y) can settle to constants.
Why It Matters
A BGP is useful as:
- a benchmark for long-run projections (what growth looks like without temporary convergence effects),
- a way to separate permanent growth drivers (productivity) from transitional ones (temporary capital deepening),
- a tool for thinking about how shocks or policy changes shift the economy temporarily away from its long-run path.