How can this be ?

I am told by liberals that the economy is in the dump due to Bush , and tax cuts . How can the deficit be getting smaller ? According to an article in The Christian Scientist Monitor , the US deficit is shrinking towards half of its 1970 levels when analyzed as a percentage of gross domestic product .
Here are some snippets from the article -http://www.csmonitor.com/2007/0221/p01s03-usec.html

Despite the ongoing costs of US military campaigns in Iraq and Afghanistan,
the outlook for the federal budget has grown substantially brighter.
Tax
revenues are rising much faster than spending, according to Treasury Department
numbers released last week. The recent trend is strong enough that, were it to
continue, the budget could move into surplus in barely a year, one economist
calculates.
In the MonitorThursday, 02/22/07



Already,
the federal deficit is shrinking toward about half the size that it has averaged
since 1970, when analyzed as a percentage of gross domestic product.
The
shift reflects a strong economy, with higher incomes and corporate profits
generating a bigger flow of tax revenue. In turn, the Treasury's progress could
help the economy by buoying investor confidence in the nation's fiscal position.