The average performance of your herd is what determines the efficiency of your swine program. Here are some guides developed at Iowa State that can help you follow and possibly improve the progress of your herd.
Hays, Virgil W.
"How Well Do Your Pigs Measure Up?,"
Iowa Farm Science: Vol. 15
, Article 2.
Available at: http://lib.dr.iastate.edu/farmscience/vol15/iss11/2