Wealthy nations with the highest rate of immigration over the past 35 years reaped a large economic benefit, and many could still absorb more workers, according to research to be presented at a top European Central Bank conference next week. Political tensions over immigration have been on the rise in recent years as far-right, anti-immigrant parties have helped drive the issue to near the top of the political agenda while making headway in countries including the US , Germany and Britain . The study, which looked at data in dozens of rich countries in the Organisation for Economic Co-operation and Development (OECD), said growth and productivity were both likely to have been boosted sharply by the influx of immigrants, most of whom were highly skilled, despite any political claims to the contrary.