In 2017, the World Bank found that the fastest growing economy in the world was Ethiopia. They calculated this by looking at the GDP growth in Ethiopia. In 2017, Ethiopia will have experienced growth of 8.3%. This is much higher than the world average growth, which is a mere 2.7%. Commentators suggest that the reason for this huge growth is that the Ethiopian government has been spending much more on infrastructure in recent years.
Other countries to watch include India. India is, in 2017, the fourth fastest growing economy in the world. There is not just one single factor at play in stimulating economic growth in India. Modi’s economic policies are one reason, but another reason is that India has the world’s largest youth population. This means that India has a very large active work force that is able to sustain large amounts of economic growth.
Wikipedia link to GDP growth for different countries in the world: https://en.wikipedia.org/wiki/List_of_countries_by_real_GDP_growth_rate