Complex sentence: Social conditions, the standard of living, and the self-confidence of the workers gradually improved due to industrialization between 1870--1916, but, while the standard of living rose among the common people, the rift between rich and poor deepened markedly.
Split into simpler sentences: Social conditions, the standard of living, and the self-confidence of the workers gradually improved due to industrialization between 1870--1916. However, while the standard of living rose among the common people, the rift between rich and poor deepened markedly.