We introduce a quantitative comparison of the overall initiation efficiency for a library of eight mono-, bis-, and tetraacylgermane visible light photoinitiators with p-methoxy and fluorine substitution patterns. Specifically, cocktail experiments were carried out, fusing pulsed laser polymerization (PLP) of methyl methacrylate (MMA) with subsequent high-resolution electrospray mass spectrometry (ESI-MS) analysis. The overall initiation efficiency reflects all critical events leading to macro-molecular growth, i.e., from light absorption and cleavage of the initiator to radical initiation. Importantly, we show that the obtained overall initiation efficiencies are self-consistent when going from lower to higher substituted systems, evidencing the validity of the derived overall initiation efficiencies within the error margins of the experiment. Remarkably, the comparison of mono-, bis-, and tetraacylgermanes reveals a nonstoichiometric increase of 40-90% in the overall initiation efficiency with increasing number of benzoyl moieties per initiator (size dependence), e.g., a maximum value of 7.6 +/- 1.8 for tetrabenzoylgermane versus benzoyltrimethylgermane. In addition, the size dependence observed for acylgermanes scales with the n pi* extinction coefficients with the number of benzoyl moieties of the respective photoinitiator. Finally, with increasing system size of the acylgermanes, a more complex channel branching-as suggested from time-dependent density functional theory (TDDFT) calculations-results in substitution-dependent intersystem crossing (ISC) and cleavage quantum yields.