Table 2 Scenario assumptions of GDP projection.

Fertility

HighFer

The HighFer scenario assumes effective fertility policy, with total fertility rate (TFR) increasing to the ideal value of 1.8 by 2050 and remaining constant thereafter²⁹.

MedFer

The MedFer scenario assumes that fertility policy prevents a decline in TFR, but the rate remains constant at 1.3 until 2100²⁹.

LowFer

The LowFer scenario assumes TFR drops to 0.7 by 2050, gradually increasing to 0.9 by 2100²⁹.

Technological development

HighTech

The HighTech scenario assumes high technological advancement, with a long-term TFP growth rate of 1.0%⁶, high level of TFP growth with 30% higher convergence rates, and long-term capital output elasticity of 0.4.

MedTech

The MedTech scenario assumes that frontier long-term TFP growth rate is 0.8%, convergence parameter ranges 0.001–0.005, and long-term output elasticity of capital is stable at the level of 0.35⁶.

LowTech

The LowTech scenario assumes the frontier long-term TFP growth rate as 0.6%⁶, lower level of technological exchange between cities with 30% lower convergence rates, and transition time ranging 10–70 years. Additionally, the long-term output elasticity of capital is assumed to be stable at 0.3.

Intercity interaction and disparities

HighInter

It is characterized by stable migration consistent with 2010 levels before 2020, then gradually decreasing to zero. The labor force participation rate (LFPR) experiences a steady decline of −0.26% before stabilizing in 2030³². Key features include uniform convergence parameters across all city tiers and extended technology transfer windows with transition time ranging 25–65 years, promoting balanced economic development through enhanced knowledge spillovers and reduced regional disparities.

MedInter

Representing a business-as-usual (BAU) reference case, this scenario assumes intermediate levels of technological exchange between cities, reflected in tier-dependent convergence rates. Non-core cities exhibit 20% lower migration attractiveness compared to core cities⁶. While migration rates increase before 2020, mirroring historical trends, employment levels experience a steady decline. The scenario captures moderate spatial inequality with controlled divergence.

LowInter

This scenario reflects constrained technological diffusion, shortened technology transfer windows with transition time ranging 15–55 years, and amplified convergence rate disparities across city tiers. Small and medium-sized cities face disproportionately large migration outflows before 2020, while the overall employment rate declines rapidly (−0.51% annually) until stabilization in 2030. The outcome demonstrates sharply widening intercity development gaps, simulating fragmented regional growth patterns.