Franklin's view of the economic disabilities of slavery is best expressed in _Observations Concerning the Increase of Mankind, Peopling of Countries, Etc._ (1751). Arguing against British restraint of colonial manufactures, he observed that "'tis an ill-grounded Opinion that by the Labour of slaves, _America_ may possibly vie in Cheapness of Manufactures with _Britain_. The Labour of Slaves can never be so cheap here as the Labour of working Men is in _Britain_."[i-188] With arithmetic based on empirical scrutiny of existing conditions, resembling the mode of economists following Adam Smith, he charged that slaves are economically unprofitable due to the rate of interest in the colonies, their initial price, their insurance and maintenance, their negligence and malevolence.[i-189] In addition, "Slaves ... pejorate the Families that use them; the white Children become proud, disgusted with Labour, and being educated in Idleness, are rendered unfit to get a Living by Industry."[i-190] Slaves are hardly economical investments in terms of colonial character. Looking to the "_English_ Sugar _Islands_" where Negroes "have greatly diminish'd the Whites," and deprived the poor of employment, "while a few Families acquire vast Estates," he realized that "population was limited by means of subsistence,"[i-191] which foreshadowed the more pessimistic progressions of Malthus. Having just maintained that "our People must at least be doubled every 20 Years,"[i-192] and intuitively suspecting that the means for subsistence progress more slowly, he exclaimed, "Why increase the Sons of _Africa_, by planting them in _America_, where we have so fair an Opportunity, by excluding all Blacks and Tawneys, of increasing the lovely White and Red?"[i-193] He saw mere economic extravagance as the short-time effect of slavery; he feared that the long-time effect would be to create an aristocracy subsisting at the head of a vast brood of slaves and poor whites.[i-194] It was inevitable in a state having no staple crop, such as rice, sugar, tobacco, or cotton, which offered at least economic justification for negro slavery, that abolition of slaves should be urged partially on purely economic grounds, and that Pennsylvania should have been the first colony to legislate in favor of abolition, in 1780. Although one may feel that economic determinism is overly simple and audacious in its doctrinaire interpretations, one can not refuse to see the extent to which economics tended to buttress humane and religious factors in Franklin's mind to make him a persuasive champion of abolition.[i-195]