These are the 5 largest mega-mergers so far in 2019

• Merger and acquisition volume slowed significantly in the third quarter of 2019, while the average deal size has swelled this year, according to new data from Mergermarket. 
• Despite the slowdown last quarter, there still have been several massive deals inked this year set to reshape industries including defense and pharmaceuticals. 
• Here are the five largest mega-mergers so far in 2019, according to data from Mergermarket. 
• Visit the Business Insider homepage for more stories.

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Dealmakers across the world have secured $2.49 trillion worth of mergers and acquisitions during the first three quarters of 2019, according to new data from Mergermarket. 

But the seemingly massive figure is still down 11.4% from the level of deal volume seen at this time last year. M&A activity also slowed considerably more during the third quarter, falling 21.2% to $622 billion. 

The average deal size rose to $424.6 million, up from $380.1 million last year and the highest on record, based on Mergermarket data suggesting dealmakers are seeking fewer, larger transactions. 

"Whether they are motivated by the desire to get more growth, or a way to secure future survival, deals are getting larger," global editorial analytics director Beranger Guille said in the report. 

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Guille continued: "On the back of the longest equity bull market in history, and amid persistently low interest rates, corporates have ample cash reserves and appealing debt financing options at their disposal to pursue M&A." 

Here are the 5 largest mega-deals of 2019, listed in increasing order of size, according to Mergermarket: 

5. Occidental Petroleum + Anadarko Petroleum

Tickers: OXY, APC

Sector: Energy 

Deal value: $54.4 billion

Source: Mergermarket

4. Saudi Aramco + Saudi Basic Industries Corporation

Sector: Industrials and chemicals

Deal value: $70.4 billion 

Source: Mergermarket

3. AbbVie + Allergan

Tickers: AGN, ABBV

Sector: Pharmaceuticals

Deal value: $86.3 billion

Source: Mergermarket

2. United Technologies + Raytheon

Tickers: UTX, RTN

Sector: Defense

Deal value: $88.9 billion

Source: Mergermarket

1. Bristol-Myers Squibb + Celgene

Tickers: BMY, CELG

Sector: Pharmaceuticals

Deal value: $89.5 billion

Source: Mergermarket