PurposeDespite the global success of Lean Six Sigma (LSS) operations, they are frequently criticised for failing to improve a company’s financial performance. This study investigated and contrasted the financial advantages of LSS, Industry 4.0 (I4.0) and Lean Six Sigma 4.0 (LSS4.0) practices in China and the United States.Design/methodology/approachWe conducted statistical analyses using online databases. We applied regression analysis to quantitatively analyse 32,813 responding organisation data from 3,691 A-share manufacturing companies in China and 5,931 responding organisation data from 570 publicly traded manufacturing firms in the United States.FindingsThis study discovered the following findings: (1) American companies are paying less attention to LSS, which is gradually becoming more important in Chinese business strategy. (2) There is a strong positive relationship between LSS implementation and financial performance in China. Nonetheless, the financial impact of LSS is less significant in post-industrial countries such as the United States. (3) There is compelling evidence in the Chinese context for the significant impact of higher LSS maturity levels on the financial performance of publicly traded manufacturing firms. However, the financial benefits of higher LSS maturity levels in the United States are less pronounced. (4) Despite frequent discussions in China and the United States, implementing I4.0 and related technologies has yet to yield the desired results, particularly in the United States. (5) LSS4.0 significantly improves organisational financial performance.Originality/valueThis study explored the impact of LSS, I4.0 and LSS4.0 on financial performance and conducted an international comparative study from a big data perspective.