The Fieldays 2015 Economic Impact report reveals the events contributes $166m to the GDP of New Zealand and $53m to Waikato.
Dr Warren Hughes of the University of Waikato Management School's Institute of Business Research and Hughes Economics independently prepared the report.
"When preparing the impact study, we look at three sources — visitor spending, equipment spending and organisation spending," says Hughes.
The decrease in both Waikato and New Zealand's revenue and GDP of 13-14% has been attributed to the dairy forecast.
"Unfortunately, as we came into Fieldays, we knew there was bad news ahead in the dairy sector and equipment purchase fell directly, and the overall total price fell accordingly," say Hughes.
However, he says all other sectors, including sheep, beef, horticulture and wine, are on the up.
"We're thrilled with the economic impacts of Fieldays 2015," says NZ National Fieldays Society CEO Jon Calder.
Calder says the event is "more than just four days in June".
"We're incredibly proud to have such relationships with our stakeholders and customers to be able to contribute so significantly to New Zealand's primary sector."