GDP(PPP, Purchasing power parity; international dollars) from 1990 to 2024 is from IMF (see website: https://www.imf.org/external/datamapper/PPPGDP@WEO/OEMDC/ADVEC/WEOWORLD.)

Now the data is available here. https://www.imf.org/external/pubs/ft/weo/2020/01/weodata/weoselgr.aspx

why did I use PPP?
Actually, in this data source, there are many types of GDP and I just picked PPP as an explanatory variable since it eliminates the effect of exchange rates changes. In fact, in the first time when I ran regression, I used the normal one and found that I needed to add year dummy to some countries. While using PPP, I did not need to use year dummy. I attribute this phenomenon to exchange. From IMF, there are many reliable databases which can be used in the future. How we can get GDP, PPP till 2050 is shown in details.

Definition of PPP:
Real GDP is the real value of goods and services produced in an economy in a time period which is generally a quarter or a year. … This amount thus calculated is termed as Real GDP. PPP or purchasing power parity is a theory which compares the prices of goods and services in different countries.