$40tn
30
20
10
US national debt
0
1970
1980
1990
2000
2010
2020
$40tn
30
20
10
US national debt
0
1970
1980
1990
2000
2010
2020
$40tn
30
20
10
US national debt
0
1970
1980
1990
2000
2010
2020
$40tn
30
20
10
US national debt
0
1970
1980
1990
2000
2010
2020