Spectroscopic factors are fundamental quantities in nuclear physics. They have been extensively used in understanding the single-particle properties of nuclear structures and astrophysical network calculations. Neutron spectroscopic factors of 88 ground state and 565 excited states for Z=3−28 stable nuclei from (d, p) and (p, d) transfer reactions have been extracted using a systematic approach with minimum assumptions. This extensive set of data suggests that the extracted spectroscopic factors are in good agreement with the predictions of the large-basis shell-model predictions. We have extended the analysis to the experimental data obtained from inverse neutron transfer reaction of proton-rich ³⁴Ar and neutron-rich ⁴⁶Ar. The experimental results show little reduction of the ground-state neutron spectroscopic factor of the proton-rich nucleus ³⁴Ar compared to that of ⁴⁶Ar. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions and the dispersive-optical model analysis, but are inconsistent with the trends observed in knockout reaction measurements.