Italy Economic growth Panel data CO2 emissions Panel Public expenditure economic growth EU Machine Learning Machine learning Time series EMU GDP Government size Ricardian equivalence Time-series energy use panel data time series Air pollution China Israel Public finance time-series APEC Artificial Neural Networks BARS curve Brazil COVID-19 Causality Climate change Covid-19 Electricity consumption Energy consumption Energy use Fiscal Policy Fiscal policy Fiscal sustainability Government debt Internet usage Musgrave-Rostow model O'Connor's model Public debt Public deficit Renewable energy Twin Deficits Twin deficits Wagner's Law Wagner's Law capital stock