There is no way to answer this question with any great degree of certainty and accuracy. The level of poverty around the world has certainly dropped, but there is no way to know how much credit the World Bank should get for this result. The World Bank is by no means the only entity trying to reduce global poverty. There are, just to name two examples, individual rich countries and many non-governmental organizations that are working to reduce poverty in the developing world. So, when poverty declines, do we credit the World Bank, aid from the US and other countries, or organizations like the Gates Foundation? Alternatively, do we credit global capitalism, which seems to have done the most to reduce poverty in China?
Therefore, all we can really say is that levels of poverty have dropped (though there is still plenty of poverty) and that the World Bank must get some of the credit.