That’s one way to slice the numbers. There are others.

In early August, 2007, Rudy Giuliani announced he was making "12 Commitments to the American People," including a pledge to "increase adoptions, decrease abortions and protect the quality of life for our children."

It's a point he has made before. During the May 3, 2007, Republican debate, he said this: "When I was mayor of New York City, I encouraged adoptions. Adoptions went up 65-70 percent; abortions went down 16 percent."

Indeed, abortions in Gotham declined 16.8 percent during Giuliani’s eight-year tenure, according to the Centers for Disease Control and Prevention.

But his claims about adoptions are far less clear-cut. The campaign didn't offer any research showing that rising adoption rates cause lower abortion rates, and we couldn't find any, either.

Two years into his first term, Giuliani created the Administration for Children's Services with a mission to improve the lives of the city’s children. The agency aims to help kids in foster care, and it measures its success in large part by how many adoptions it facilitates each year. We focus on page 14 of the ACS 2003 Year End Review, which shows a bar chart of adoptions conducted through the city’s child welfare system from 1989 to 2003.

Giuliani was mayor from Jan. 1, 1994, to Dec. 31, 2001. His new agency came on line in January 1996.

The chart shows a gradual increase in adoptions from 1989 through 1994, then a steeper increase through 1997 — the middle years of Giuliani's tenure. After that year, the numbers decline through 2002.

Giuliani arrives at his 65 to 70 percent increase by taking adoption rates for the six years before ACS was created and comparing them to the six years after.

That's one way to look at it, but it conceals some things. For instance, the chart shows that if you simply compare adoption rates in the first year of his tenure and in the last year, the rate increased by only 17 percent, a point made by our friends at FactCheck.org.

Averaging the rates over two six-year blocks helps smooth out peaks and valleys in individual years caused by social, economic and other forces, campaign aides said. The first two years after ACS came on line, there was a spike in adoptions that Giuliani's campaign said was because of a backlog of foster kids waiting to connect with families. Then, the numbers leveled off.

It's true, the aides say, the numbers go down significantly in Giuliani's final two years. But they're still higher than those of his predecessor, David Dinkins.

More recently, Giuliani has used a much more flattering number than the one he started with. His staff compared adoptions in all eight of his fiscal years against all eight of his predecessors'. This works out to a whopping 133 percent increase in adoptions.

So which number is it?

Something’s wrong if voters have to ask.

When a statistic seems to go in so many directions, the best approach is an apples to apples one. For its abortion statistic, the Guiliani campaign looked at two points in time (the beginning and end of his tenure) and compared the two. Doing that for adoptions yields an increase of 17 percent.

So, he's got his numbers right on abortion rates, but he has inflated the adoption figures by getting too fancy with his math. We find his overall claim half-true.

UPDATE: We've corrected the launch date for the Administration for Children's Services. We mistakenly said 2006 when we should have said 1996.