Although his figures are correct, he doesn't include his full eight years in office.
When Giuliani took office on Jan. 1, 1994, city spending was in the hole by $700-million, according to figures provided by a former Giuliani budget director, Bob Harding, at the request of the Giuliani campaign. The budget forecast for the next fiscal year, which would begin July 1, 1994, projected a gap between revenues and spending of $2.3-billion.
Jump ahead seven years, to June 30, 2001, the end of Giuliani's last full fiscal year in office. The city wound up with the $2.9-billion surplus Giuliani is boasting about. So far, so good.
But the last budget Giuliani wrote, for the 2001-02 fiscal year beginning the next day, had higher spending with a much smaller surplus – a $350-million surplus, to be precise, as of the day he left office. And Giuliani's budget forecast for the next fiscal year, 2003, says Harding, included a deficit of $3.1-billion that Giuliani's successor, Michael Bloomberg, would have to close. After the 9/11 attacks, that projection ballooned to $4.77-billion, according to figures from the New York City Office of Management and Budget. (The figures are not adjusted for inflation.)
What Giuliani has done is include the budget that outgoing Mayor Dinkins wrote as he left office, but doesn't include the budget Giuliani himself wrote as he left office. Including both is closer to a fair comparison of the two changes of administration. It looks at (1) the moment he took office and left, and (2) the out-year projection for the first full fiscal year of the new administration as of the same date.
So Giuliani inherited a deficit of about $700-million and left a surplus of $350-million as of the first and last days of his tenure. He also inherited a projected budget gap of $2.3-billion for his next fiscal year, and left his successor, Bloomberg, a projected deficit of $4.7-billion.
It is probably worth noting that both out-year "deficit" figures – the one Giuliani says he inherited from Dinkins and the one he bequeathed to Bloomberg – are just projections. The city (unlike the federal government) is not allowed to end the year with an operating deficit. Harding notes that gaps in out-year budgets have often happened in New York City and have, through a combination of above-budget revenues or below-budget spending, gotten into balance or turned to surplus by the time the year ends.
Add it all up and we only get halfway to true.