The historical share of Manufacturing GDP is from World Bank (see website: https://data.worldbank.org/indicator/NV.IND.MANF.ZS ).

The shortage of this source is that there is not forecast till 2050. In fact, no institution on the Earth has forecast till 2050 on how much manufacturing GDP of the total. But fortunately, we know the total GDP till 2050 and the percentage of manufacturing GDP will not change rapidly in the short run (though GDP and population are not going to change suddenly either).

Based on the assumption that percentage of manufacturing in developed countries will be decreasing slightly and that in developing countries will be increasing slightly in next 10 or 20 years (it depends on different countries) and will be increasing more slightly (even be decreasing) after 2040, which can be explained as industry transfer, we can get growth rate of the percentage of manufacturing of total GDP. Then we can the percentage of manufacturing and manufacturing GDP (value, added)