Penn World Table: https://www.rug.nl/ggdc/productivity/pwt/
World Bank: https://data.worldbank.org/
US Economic Data: https://www.nber.org/releases/
IMF Data: https://www.imf.org/en/Data
Economic Policy Uncertainty Indicator: http://www.policyuncertainty.com/
Economic Indicators: https://tradingeconomics.com/indicators
Nowcasting: https://www.now-casting.com/home
US Economic Data (FRED): https://research.stlouisfed.org/fred-addin/