  Many active galactic nuclei (AGN) show strong variability of the optical
continuum. Since the line flux, profile shapes and intensity ratios are
changing, we analyze the variability patterns and possible periodicity of Type
1 AGN NGC 5548, using the Eigenvector 1 (EV1) diagram in different variability
states, taking advantage of very long term monitoring campaign data. The
preliminary results suggest that NGC 5548 - a highly variable object that over
several decades has shown large amplitude continuum fluctuations and flaring
behavior - remains Pop B. This means that the range in Eddington ratio, even
when the source is in a bright state, remains consistent with the value of the
low accreting Pop B. We inspected EV 1 parameters of a single object though
long term monitoring, assuming an inclination and black hole mass to be
constant during the observational time. Our results imply that the main driver
for the variations along the EV 1 diagram could be dimensionless accretion
rate. If so, then it appears that the source never crossed the boundary for
structural changes, indicatively placed at $L/L_{Edd} \sim$ 0.2.
