The federal budget deficit hit $598 billion in the first half of the 2018 fiscal year, according to the Congressional Budget Office, quickly outpacing the deficits of recent years.

At the same point in 2017, the deficit was $78 billion lower. That year, the entire deficit amounted to $666 billion, just 11% higher than the amount the U.S. government had to borrow in the first half of 2018.

The fast-increasing deficit expanded as government outlays grew 2.5 times faster than revenues. On the revenue side, which was up 2 percent over last year, the GOP tax reforms ate into individual tax revenue, and slashed corporate tax revenue by $22 billion, or 22 percent.

On the spending side, Social Security outlays increased $19 billion, or 4 percent, while interest payments on debt increased $18 billion, or 12 percent. Meanwhile, disaster relief efforts drove Homeland Security spending up $14 billion, a 56 percent increase. Defense spending also rose $12 billion — a 4 percent increase.

Budget-watchers have warned that the combination of the massive, unfunded tax cut the GOP passed last year and a spending deal that busted through preset budget caps would lead the U.S. deficit past $1 trillion by 2019.