The Convergence Speed in Solow Growth Model

The speed of convergence in Solow growth model is

Δk/k=-λ[ln(k)-ln(k*)],

Δy/y=-λ[ln(y)-ln(y*)],

where λ≡(1-α)(n+g+δ).

"n+g+δ is typically about 6% per year (1-2% population growth, 1-2% growth in output per worker, and 3-4% depreciation). If capital's share is roughly one-third, λ is thus roughly 4%. k and y therefore move 4% of the remaining distance toward k* and y* each year, and take approximately 18 years to get halfway to their balanced-growth path values."

Romer, "Advanced Macroeconomics"