Members of Amazons Prime service are three times as likely to make frequent purchases from the online retailer.

Thats according to a study by RBC Capital, which found that 73 per cent of Prime members in US shop at Amazon at least two times a month – compared to just 22 per cent for non-members.

49 per cent of members spend over $800 on Amazon annually, compared to while only 16 per cent for non-Prime customers.

74 per cent of Prime members said they used Amazon more today than when they first joined Prime, and members spending seems to increase over time too. Of people who have been members for over four years, 68 per cent spend over $800, compared to 41 for those in their first year of membership.

Having started out as a free delivery subscription service in 2015, Prime has evolved to include video and music streaming, as well as cloud storage, for an annual cost of $99 (£79 in the UK). In the US, 40 per cent of Amazons customers are now members of the scheme, compared to 25 per cent in 2013, with a estimated total of 60-80m Prime members worldwide.