Here is a look at U.S. merger and acquisition activity going back to 2000. Number of deals and value are listed. Deals peaked in 2007, just before the Great Recession.

2000: 10,472 deals; total value of $1.5 trillion.

2001: 8,216 deals; total value of $794 billion.

2002: 7,429 deals; total value of $470 billion.

2003: 7,416 deals; total value of $572 billion.

2004: 8,253 deals; $852 billion.

2005: 8,220 deals; $1.2 trillion.

2006: 10,238 deals; $1.5 trillion.

2007: 10,695 deals; $1.6 trillion.

2008: 8,778 deals: $1 trillion.

2009: 7,415 deals: $803 billion.

2010: 10,108 deals; $898 billion.

2011: 10,518 deals; $1 trillion.

2012: 12,192 deals; $982 billion.

Source: Financial data service Dealogic.