The launch of the Solar Dynamics Observatory (SDO) with the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) instruments, became the first time that both a vector magnetograph and ribbon-imaging capabilities became available on the same observing platform. This combination presented a first chance to do statistical studies of the properties of the vector magnetic fields participating in the flare. Here we present a statistical analysis of spatial and temporal properties of the vector magnetic fields in 40 active regions associated with flares, of GOES class C9.0 and greater. For every event in the database, we use 1) a sequence of HMI/SDO vector magnetograms, to track magnetic field properties before and after the flare and 2) a sequence of AIA 1600A images, to track location of flare ribbons. We calculate the following physical properties of the photospheric vector magnetic field within the active region, flare ribbons and the polarity inversion line: magnetic shear, vertical electric current, current neutralization, free energy proxy etc. We present the results and discuss their meaning in the context of the standard flare model.