The role of the federal government has been squarely at the center of the national debate the last few months.

But who are the people who comprise that system of government?

Judy Woodruff set out for answers in her ongoing series, America at a crossroads.

160 feet below the surface, my team and I got a crash course on the history of coal mining,

and what was once one of the leading causes of death in mines.

And this square is coal that has not been mined.

That's what's keeping the mountain over our heads.

Christopher Mark spent his life's work trying to prevent roof collapses in coal mines.

He worked for the U.S. Department of Labor's Mines Safety and Health Administration, but was

speaking to us as a private citizen.

When I started looking at the data, saying let's just not look, you know, kind of in general

at what the coal industry thinks is important, let's look at what's really killing people.

Mark began his career underground in 1976, working as a coal miner himself in West Virginia,

after graduating from high school in Princeton, New Jersey.

He later went on to get a Ph.D. in mining engineering and now lives near the Tour Edmine

and museum we visited together, just north of Pittsburgh.

Part of the problem was that the engineers who had been attacking this problem had been looking at it with an engineering mindset.

But Mark took that mindset and combined it with statistics to create new software that's credited with saving an untold number of lives.

Mark and his work are one of the stories in a new book edited by best-selling author Michael

Lewis, Who is Government, the untold story of public service.

It's based on a Washington Post series written by Lewis and six other authors.

It's sort of like all the mess that the private sector can't solve, it is really hard to

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