2021: $108.5 billion
2020: $75.5 billion
2019: $59.7 billion
2018: $51.0 billion
2017: $35.7 billion
2016: $29.1 billion
2015: $22.7 billion
2014: $19.7 billion
2013: $16.1 billion
2012: $13.2 billion
2011: $9.9 billion
2010: $7.1 billion
2009: $4.9 billion
2008: $4.1 billion
2007: $3.0 billion
2006: $2.3 billion
2005: $1.9 billion
2004: $1.5 billion
2003: $1.1 billion
2002: $847 million
2001: $700 million
2000: $574 million
1999: $294 million
1998: $87 million
1997: $16 million