The table shows receipts (income) and outlays (spending) in billions of dollars for the U.S. government in selected years.
$$
\begin{array}{|c|c|c|}
\hline \text { Fiscal Year } & \text { Receipts } & \text { Outlays } \\
\hline 2001 & 1991 & 1863 \\
2006 & 2407 & 2655 \\
2011 & 2303 & 3603 \\
2016 & 3268 & 3853 \\
\hline
\end{array}
$$
During which years did the budget show a surplus? A deficit? Explain the answers.