Worst countries for takeout ...

Turkey - 50%
Venezuela - 44%
Brazil - 30%
Argentina - 28%
France - 25.7%
Japan - 25.1%

The best:
Ireland - 10.9%*
Great Britain - 11.1%*
South Africa - 11.2%*
Australia - 14%
Hong Kong - 14%

Those takeouts marked with * are via bookmakers. Those countries also have tote betting with much higher takeout, but 99% of the handle in those countries goes through the bookmakers (one of the reasons it is so expensive going to the races in UK and Ireland).

Australia also has a tote and bookmakers, but both return 86% and the handle is split fairly evenly between the books and the tote.