The new study tracked the health of 122,000 women since 1976.

Focusing exclusively on children, a more recent study tracked 81 teenagers for six years.

The study tracked the 1997 performance of 940 companies in various industries.

The study tracked tax returns of 14,000 households between 1979 and 1988.

The study tracked more than 93,000 women over four years; almost 8,000 of them had been taking statins.

Neither study has yet tracked the children through the later grades to measure the programs' actual effects on school violence.

The study tracked Chicago high school students who graduated in 1998 and 1999.

The study then tracked their health until 2002, with many of the participants getting a second screening 10 years after the first one.

The study tracked the behavior of 169 participants in the Pittsburgh area who were selected from four schools and community groups.

The study also tracked these students's progress through high school and college.