The size of the crowd attending Donald Trump's presidential inauguration may be up for debate but the number of people tuning in at home is not.

Almost 31 million viewers watched live television coverage of Trump's presidential inauguration, according to figures released by Nielsen. The viewership numbers make Trump's the second most-watched swearing-in in three decades, behind only Barack Obama's inauguration in 2009, which attracted 38 million viewers.

According to Neilsen, the inauguration was aired on 12 broadcast and cable networks with live coverage from about 10 a.m.-6 p.m. EST.

A total of 24 million households tuned into at least part of the inauguration, with the largest audience - 19 million - ages 55 and above. The fewest number of viewers - 2.8 million - were those ages 18-34.

Here are the number of people who tuned into past televised inauguration coverage, according to Neilsen.

2013 - Barack Obama - 20.6 million

2009 - Barack Obama - 37.8 million

2005- George W. Bush - 15.5 million

2001 - George W. Bush - 29 million

1997 - Bill Clinton - 21.6 million

1993 - Bill Clinton - 29.7 million

1989 - George H.W. Bush - 23.3 million

1985 - Ronald Reagan - 25.1 million

1981- Ronald Reagan - 41.8 million

1977 - Jimmy Carter - 34.1 million

1973 - Richard Nixon - 33 million

1969 - Richard Nixon - 27 million

Nixon is the only two-term president since Nielsen began tracking the data to draw a larger audience for his second inauguration than his first.

Nielsen ratings do not account for online viewing, so the actual number watching Trump take his oath of office was actually much higher.

Fox leads all networks

Fox News Channel led Inauguration Day ratings, with 11.76 million total viewers compared to 3.375 for CNN and 1.49 for MSNBC. Fox's numbers were particularly strong during the oath and inaugural address portions of the day, with 2.99 million viewers turning in for Trump's address as compared to 521,000 for CNN and 315,000 for MSNBC.