What does adam smith claim is the single greatest factor in increasing productivity?

The Wealth of Nations Summary and Analysis of Book I. Adam Smith begins by stating that the greatest improvements in the productive power of labor lie in the division of labor. Even in the production of very simple products, division of labor always increases productivity exponentially.

the declaration states, “we hold these truths to be self-evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness….”