In order to verify scenario of solar cycle suggested by Babcock and Leighton, a new index of activity is derived from observational data of bipolar spot groups by taking positions of magnetic poles of the groups into account. In agreement with the Babcock-Leighton scenario, this index reveals substantial correlation with amplitude of the axisymmetric magnetic field of the Sun measured at subsequent minimum of activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html