The intensity of business merges and acquisitions changes over time. Theoretically, competitive companies constantly seek for ways to grow, mainly due to expected economies of scale and scope. In the paper we discuss various aspects of business mergers and acquisitions in the context of market concentration. We also highlight the issue of symptoms and causes of fluctuations in economic activity. Using data for the period of 2000-2012 we analyse the value of the overall business mergers and acquisitions in connection with the global economic growth and selected stock market indices. Next, we focus on the global agro-food sector and test the hypothesis that the number and value of mergers and acquisitions in this sector were related to the business cycle fluctuations observed in the period of 2000-2010. Firstly, the results of our research show that both merger and acquisition transactions carried out in the agro-food sector had largely inter-branch or, at the most, inter-sectorial character. Secondly, a positive relationship between fluctuations in economic activity in the global agro-food sector and the intensity of mergers and acquisitions was found, especially regarding the value of those transactions, what means that economic recovery facilitates concentration processes. Thirdly, the observed connection between the directions of changes in the merger and acquisition activities and the changes in stock market indices seems to be determined by the situation on the capital markets.