This chapter looks at the evolution of merger activity. It explores the characteristics of merger regimes and the dynamics of merger notifications in the last decade, as well as merger interventions by competition authorities.
A Decade of OECD Competition Trends, Data and Insights
Abstract
The OECD, as stated in its Recommendation on Merger Review [OECD/LEGAL/0333], recognises merger control as a key component of competition regimes, as it prevents harm from anti-competitive transactions that might reduce competition. This chapter explores the last ten years of data for merger activity. It will look at trends in merger control regimes, including their characteristics, the dynamics in the numbers of mergers notified to competition authorities and the type of their decisions.
In the period 2015-2024, more than 95 000 mergers were notified to 59 jurisdictions in the CompStats database and around 91 000 decisions were made. Among these mergers, 97.98% were unconditionally cleared, 1.76% were cleared subject to remedies and only 0.25% were prohibited or challenged. During the ten years, 611 mergers were withdrawn by the parties, representing 0.65% of the mergers notified. Figure 2.1 presents the totals of key merger metrics during the decade.
Note: Data based on the jurisdictions in the OECD CompStats database that provided data for each of the variables for the period 2015-2024. The numbers presented in this figure represent global totals for the entire decade. They should not be interpreted as annual averages or compared directly with per-year, per-jurisdiction figures used elsewhere in this report.
Source: OECD CompStats database
Overall, transaction volumes have grown over the past decade. As Figure 2.2 shows, more than 12 000 mergers were notified to the CompStats jurisdictions in 2021, reaching the highest number of merger notifications in a year. This follows a drop in 2020 (due to COVID-19 as will be discussed below), when less than 9 000 fillings were made. In 2024, 9 894 mergers were notified, which represented an increase of 10.6% with respect to 2023 and a 20.5% increase with respect to mergers notified in 2015.
Note: Data based on the 59 jurisdictions in the OECD CompStats database that provided data for each of the variables for the period 2015-2024.
Source: OECD CompStats database
Global trends in mergers and acquisitions in the past ten years have been impacted by macroeconomic dynamics and the correlation between merger notifications and variables such as GDP growth, inflation and interest rates is strong. Periods of strong GDP growth tend to spur deals, while periods of recession or slower growth dampen them (see Figure 2.3). The most impactful shock in the last decade was the COVID-19 pandemic, where OECD jurisdictions observed a decrease of -4.75% in their GDP (and OECD estimates for the decrease in the World’s GDP were around 3% (OECD, 2020[14]; 2021[15]) that correlated with a drop in M&A activity in 2020 compared to 2019. This represented on average 10.3% fewer notifications, while the post pandemic rebound saw record deal volumes in 2021. This initial decline was observed in 70% of the jurisdictions in the sample, with Latin American jurisdictions being the ones that observed the biggest drop – as notifications fell more than 40% in Barbados, Ecuador, Panama and Chile. The subsequent recovery, which on average increased notifications by 40% in 2021 compared to 2020, was observed in 80% of those jurisdictions. In Latvia, the United States, Malta, the Slovak Republic and Greece, the increase was higher than 100% with respect to notifications in 2020.
After the two years with significant changes, 2022 presented a mixed picture. In OECD jurisdictions notifications decreased, although they remained higher than the pre COVID-19 period, while in non-OECD jurisdictions they increased further. A sudden increase in the number of mergers notified in 2021, which directly impact merger reviews, may have impacted the resources that authorities had to dedicate to merger reviews.1 More mergers to assess require more time and, often, a more flexible allocation of the staff from other enforcement areas. Challenges on resource allocation, case prioritisation and the interaction between increased activity in one of the areas of work and the resources dedicated to others have raised concerns from competition authorities recently.2
Note: A three-year average is used to smooth out volatility caused by random fluctuations. Data based on the 59 jurisdictions in the OECD CompStats database that provided data for merger notifications for the period 2015-2024.
Source: OECD CompStats database and World Bank
Recent literature suggests that lower interest rates stimulate transactions by reducing borrowing costs and that high inflation, particularly when prolonged, disincentivises acquisitions as profit margins are reduced (Lakra, 2024[16]; Chiriac, 2021[17]). In line with these findings, moderate inflation and low interest rates may have also contributed to the expansion of M&A activities observed both between 2015 and 2019 and in 2021. However, the interest rate hikes since 2022, which reduced liquidity and made debt more expensive, may have contributed to the decline of activity observed in 2022 and 2023. Together with more elevated inflation rates, slower global economic activity, increased macroeconomic uncertainty and heightened geopolitical tensions, negative growth rates were observed for mergers between 2022 and 2024.
Trade policies and geopolitical dynamics also have an impact on deal flows. Conflicts, tensions and even elections generate wait-and-see dynamics where firms pause deals amid tariff and regulatory swings (OECD, 2025[18]). Should geopolitical tensions ease and interest rates fall, the world could see a new wave of merger activity, pushing competition authorities to gear up for a potential flood of filings.
The majority of mergers assessed by competition authorities do not have a significant impact on competition. This is reflected in the percentage of mergers being cleared without any remedy (94.6% on average, per jurisdiction, per year). However, despite increases in the levels of mergers notified in the past decade, competition authorities have maintained relatively stable intervention levels, which include conditionally approving mergers, challenging or prohibiting them (according to the applicable legal regime). The average intervention rate during the decade was 5.39% with a peak of 6.87% in 2017 and values for the beginning and the end of the decade close to 4.8% (see Figure 2.4). When looking at jurisdiction-level intervention rates and their evolution during the decade, it is possible to see that in 23 jurisdictions the intervention rate showed an increase while in the other 25 it decreased. Six jurisdictions observed stable levels of intervention, as in the aggregate case (see Figure A B.3).
Note: The intervention rate is the share of mergers approved with remedies, prohibited or challenged over total merger decisions. A three-year average is used to smooth out volatility caused by random fluctuations. Data based on the 54 jurisdictions in the OECD CompStats database that provided data for merger remedies and merger prohibitions or challenges for the period 2015-2024.
Source: OECD CompStats database
Notably, the number of mergers prohibited or challenged increased as a proportion of total decisions, particularly in OECD jurisdictions, where most prohibition decisions are concentrated (see Figure 2.5). 2024 was the year with the most prohibited or challenged mergers as a proportion of total merger decisions. As observed in the 2024 version of the Competition Trends report, an analysis of 216 prohibition or challenge decisions between 2015 and 2022 revealed that theories of harm based on unilateral, horizontal effects make up the majority of these decisions (OECD, 2024[19]). Prohibition decisions in non-OECD jurisdictions are relatively rare, representing less than 0.1% of merger decisions in 2024.
Note: A three-year average is used to smooth out volatility caused by random fluctuations. Data based on the 58 jurisdictions in the OECD CompStats database that provided data for merger prohibitions or challenges for the period 2015-2024.
Source: OECD CompStats database
These prohibition dynamics are not specific to a single jurisdiction. Although the number of jurisdictions has shown an upward trend over the past decade, as shown in Figure 2.6 left, prohibitions and challenges are more common in OECD jurisdictions. During the ten-year period, five jurisdictions (United States, United Kingdom, Israel, Australia and Mexico) accounted for 45% of the mergers prohibited or challenged (see Figure 2.6 right). 2024 was the year with the most prohibitions, with 20 jurisdictions having prohibited or challenged at least one merger.
Note: Data based on the 58 jurisdictions in the OECD CompStats database that provided data for merger prohibitions or challenges for the period 2015-2024.
Source: OECD CompStats database.
The increase in the number of mergers challenged or prohibited, despite a significant increase in overall decisions, may suggest that competition authorities continue to identify and act upon anticompetitive mergers. Several factors could be potentially contributing to this trend, including rising levels of concentration in many industries,3 and an increased attention to non-price effects of mergers. The OECD Competition Committee had discussed many of these issues in the past decade. For example, it has explored the existing and potential new tools required to effectively scrutinise problematic mergers in increasingly concentrated markets, such as the use of market-share or transaction-value based thresholds, powers to review ex officio some transactions and market intelligence mechanisms (OECD, 2018[20]).
The past decade has also seen competition authorities reviewing more non-price effects of mergers in the markets which could have resulted in more mergers being challenged or prohibited. Conversations at the OECD on dynamic competition and innovation, for instance, illustrate the importance for competition authorities to capture all possible effects that transactions may have on competition (see OECD (2023[21]; 2021[22]; 2018[23])).
Contrary to prohibitions, the average proportion of mergers cleared with remedies shows a slightly decreasing trend, as observed in Figure 2.7.4 However, the evolution at jurisdiction level is mixed. In 23 of the jurisdictions in the sample, the share of mergers cleared with remedies observed an increasing trend during the decade, while in 26 it decreased. In two jurisdictions (Colombia and Poland), it remained constant. Moreover, around 70% of the jurisdictions in the sample cleared at least one merger with remedies every year, which highlights their constant use.
Note: A three-year average is used to smooth out volatility caused by random fluctuations. Data based on the 59 jurisdictions in the OECD CompStats database that provided data for merger clearances with remedies for the period 2015-2024.
Source: OECD CompStats database
One key variable that also reflects indirectly on the intervention by competition authorities is the number of withdrawn notifications, as merging parties may anticipate a prohibition decision by withdrawing their notification. While this number remains low, it seems to have increased significantly over the period 2023‑2024. United States, France, Israel, Brazil and Germany accounted for 38% of all withdrawn merger notifications during the decade. While the reasons for the increased number of withdrawn notifications may vary across jurisdictions and are not always evident to the authorities, new frameworks – such as foreign direct investment (FDI) screening, foreign subsidies regulations and national security rules – that have been introduced, may have further intensified oversight of these transactions. An OECD Roundtable held in 2022 on the topic identified that these reviews are often complementary to competition reviews and may impact the final outcome (OECD, 2022[24]). In future research, it is worth exploring the extent to which there is a link between introduction of these frameworks, intervention by authorities, withdrawn notifications and future merger notifications.
The following table presents yearly growth rates of the most relevant merger variables, reflecting the dynamics described above.
Note: Data based on the jurisdictions in the OECD CompStats database that provided data for each of the variables for the period 2015-2024.
Source: OECD CompStats database.
The past ten years have seen some level of alignment in the characteristics of merger regimes across CompStats jurisdictions, as shown in Figure 2.8. While all OECD jurisdictions, with the exception of Luxembourg, had a merger regime in place before 2013, some non-OECD jurisdictions have put in place a merger regime for the first time after 2015.5 Moreover, some jurisdictions have amended their laws with significant changes to the structure of their regimes, such as going from voluntary to mandatory notification systems, from post to pre-merger reviews or from a single to a two-phase procedure. Other amendments in the past decade have focused on specifying timeframes for review, introducing simplified procedures, clarifying standstill obligations or establishing filing fees (see the 2021 edition of CompTrends for a detailed analysis on these trends (OECD, 2021[25])). Currently, the characteristics of the merger regimes seem to have generally aligned into mandatory pre-merger notification systems with two review phases, as it can be seen below. The existence of a simplified procedure for transactions that are unlikely to raise competition concerns is also a common feature of regimes, with 63% of the jurisdictions in the sample having one.
Notes: In November 2024, Australia passed a legislation that introduces a mandatory notification system. However, given that the system will only be in place since 2026 and that this report covers the period 2015-2024, Australia’s regime is presented in the figures as voluntary.
Pre-merger’ regimes refer to those considering mandatory or voluntary filings before the transaction is consummated, while ‘post-merger’ regimes consider filings after the merger has been completed. Some jurisdictions incorporate both pre- and post-merger filing considerations, depending on specific criteria.
Source: OECD CompStats database and CompStats authorities’ websites.
The majority of the jurisdictions have turnover thresholds, often complemented with other criteria such as transaction value (see Figure 2.9). The last decade has observed merger guidelines’ amendments or issuance of guidance specific to the calculation of notification thresholds, clarifying how to calculate values and determine whether a merger must be notified.
Note: Some jurisdictions have multiple notification thresholds, using more than one of the criteria. This graph includes regimes with voluntary notification that has defined jurisdictional test for when a merger could qualify for review.
Source: OECD CompStats database and CompStats authorities’ websites.
The continued alignment on procedure aspects and merger regime characteristics is further demonstrated by the latest revision of the OECD Recommendation on Merger Review, in 2025, that considers internationally best practices in merger review and analysis (see Box 2.1).
The OECD Recommendation on Merger Review [OECD/LEGAL/0333], adopted by the Council in 2005, was revised in June 2025 aiming to contribute to greater convergence of merger review procedures and analysis towards internationally recognised best practices. It recognises key developments on procedural and substantive matters that have led to greater convergence. The main elements of its revision are:
the strengthening of principles related to merger review framework, notification and review procedures
the inclusion of principles to guarantee reliance on a clearly defined framework to ensure that merger assessment is effective and transparent
the focus on the provision of clear guidance for the design, assessment and adoption of merger remedies, as well as on co-operation between reviewing jurisdictions on remedy design and implementation in transnational mergers
the encouragement to perform ex-post assessment of merger decisions and remedies.
Within the principles that cover merger review procedures, the revision acknowledges the importance of clear definitions of reviewable mergers, as well as calculations of merger notification thresholds and jurisdictional tests; the adoption of standstill obligations in ex-ante, mandatory regimes; and the consideration of simplified procedures for transactions that do not raise competition concerns.
Source: OECD, Recommendation of the Council on Merger Review [OECD/LEGAL/0333], https://legalinstruments.oecd.org/en/instruments/OECD-LEGAL-0333.
← 1. A review of merger investigations and decisions reveal a very strong positive correlation of 0.99.
← 2. Given the need to share experiences and better practices on this issue, the topic will be discussed during the next Competition Committee meeting in June 2026.
← 3. There has been a wide variety of academic literature that presents robust evidence that industry concentration has risen over the past decades. In February 2025, Calligaris et al. ( (2025[45]) published a working paper on Concentration and business dynamics in product markets. The paper aimed to measure concentration across product markets in Europe and concluded that product and industry concentration increased in Europe between 2012 and 2021. See also Koltay, Lorincz and Valletti (2023[46]).
← 4. It is important to note that this trend differs to the trend highlighted in previous editions of the OECD Competition Trends report due to a change in the sample that significantly impacted the trend.
← 5. The most recent one was Peru, introducing its merger regime in 2021.