Background and objective: Globally there continues to be a steady increase in the area
commercially cultivated with genetically modified (GM) crops. Alongside this, many
publications have reported the economic impacts of GM crop cultivation, finding large
variability in farm-level economic impacts between and within countries, across years, and
between different crop/trait combinations. Variability may be due to different pest pressures,
social, cultural and economic contexts, and seasonal variation in conditions. Policy makers
need impartial and robust appraisal of the information. This systematic review therefore aims
to answer the question: “What have been the farm-level economic impacts of the global
cultivation of GM crops?”.
Methods: The question for this review contains the following components:
(1) A Population: economic indicators recorded at the farm level
(2) An Intervention: the cultivation of any commercial GM modification
(3) The Comparator: comparison with a conventional (non-GM) cropping system
(4) Outcome: economic impacts. Change in economic indicators at the farm level
A systematic search for relevant articles was conducted using five databases and one
search engine using search statements designed to identify any study in any country
measuring economic parameters at the farm level, where there was cropping of a
commercial GM trait. All retrieved articles were scanned at title, then abstract and finally full
text level using the criteria set out below in order to select those relevant. Following the
systematic search and subsequent screening, articles were critically appraised to assess
study quality using 10 questions and a three point quality scale. Next, data were extracted
from the articles and entered into an Excel spreadsheet. Once cleaned, the data were
exported to SPSS to facilitate meta-analysis using ANOVA to conduct comparison of means.
Additional narrative synthesis of qualitative data was also conducted.
Main Results: The systematic search generated 3522 extracted titles plus 56 items from
grey literature sources. From these, 22 relevant articles were identified. The information
within these 22 articles was first assessed using narrative synthesis. Extracted monetary
values were assigned to different categories, for example, gross profit, revenue, chemical
costs, and others. The categories were examined to establish the average percentage
change recorded by each.
• Gross profits were 81% and net profits 66% higher for GM crops
• Seed costs were 97% and total variable costs 23% higher for GM crops
To facilitate further analysis, two additive categories of values were derived, namely profits
• The additive category of farm level profiti suggests there is an average increase in profit
of 75% when growing GM crops as opposed to the non-GM equivalent.
• The additive category of farm level costsii suggests there is an average increase in costs
of 40% when growing GM crops as opposed to the non-GM equivalent.
Conducting meta-analysis revealed that crop/trait combination, level of development of a
country (as measured by the Human Development Index), and date of publication were
statistically significantly related to the percentage change recorded in farm level profits and
Conclusions: Implications for policy - One of the key findings from the review is that in
every case when planting GM crops as opposed to a non-GM equivalent, there was a farmlevel
economic impact. This was particularly notable for certain economic variables, namely
gross profit and seed costs, but less significant for other economic variables such as trading
price and energy costs. The change in farm level profit was least positive in the most
developed countries. Implications for research - Overall, it is important that research
continues into conducting and reviewing farm level studies, particularly as there is some
suggestion that changes in farm level profit and costs that arise as a result of growing GM
crops as opposed to the non-GM equivalent, change through time.
Genetically modified crops; economic impact; farm; global cultivation
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