  Rapid increase of horizontal magnetic field ($B_h$) around the flaring
polarity inversion line is the most prominent photospheric field change during
flares. It is considered to be caused by the contraction of flare loops, the
details behind which is still not fully understood. Here we investigate the
$B_h$-increase in 35 major flares using HMI high-cadence vector magnetograms.
We find that $B_h$-increase is always accompanied by the increase of field
inclination. It usually initiates near the flare ribbons, showing step-like
change in between the ribbons. In particular, its evolution in early flare
phase shows close spatio-temporal correlation to flare ribbons. We further find
that $B_h$-increase tends to have similar intensity in confined and eruptive
flares, but larger spatial-extent in eruptive flares in a statistical sense.
Its intensity and timescale have inverse and positive correlations to the
initial ribbon separations, respectively. The results altogether are well
consistent with a recent proposed scenario which suggests that the
reconnection-driven contraction of flare loops enhances photospheric $B_h$
according to the ideal induction equation, providing statistical evidence to
the reconnection-driven origin for $B_h$-increase for the first time.

Solar and Stellar Astrophysics;Space Physics