v3.21.2
Income taxes - Schedule of effective tax rate (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income taxes      
U.S. Statutory rates 21.00% 21.00% 21.00%
Foreign income not recognized in USA (21.00%) (21.00%) (21.00%)
China income taxes (including Hong Kong SAR) 16.00% 25.00% 25.00%
Impact of tax rate in other jurisdictions (5.00%) 3.20%  
Impact of tax reduction of Hong Kong profits tax   4.40%  
Tax effect of non-deductible expenses (10.40%) (7.80%) (7.20%)
Valuation allowance (0.10%) (42.90%) (13.20%)
Under provision in respect of prior years (0.70%) (26.60%) (2.20%)
Other 0.60% (32.20%) (3.20%)
Effective income taxes 0.40% (76.90%) (0.80%)