Within a few years after the panic of 1837 Astor's wealth multiplied to an enormous extent. Business revived, values increased. It was now that immigration began to pour in heavily. In 1843 sixty thousand immigrants entered the port of New York. Four years later the number was 129,000 a year. Soon it rose to 300,000 a year; and from that time on kept on ever increasing. A large portion of these immigrants remained in New York City. Land was in demand as never before; fast and faster the city grew. Vacant lots of a few years before became congested with packed humanity; landlordism and slums flourished side by side, the one as a development of the other. The outlying farm, rocky and swamp lands of the New York City of 1812, with its 100,000 population became the thickly-settled metropolis of 1840, with 317,712 inhabitants and the well-nigh half-million population of 1850. Hard as the laborer might work, he was generally impoverished for the reason that successively rents were raised, and he had to yield up more and more of his labor for the simple privilege of occupying an ugly and cramped habitation. Once having fastened his hold upon the land, Astor never sold it. From the first, he adopted the plan, since religiously followed, for the most part, by his descendants, of leasing the land for a given number of years, usually twenty-one. Large tracts of land in the heart of the city he let lie unimproved for years while the city fast grew up all around them and enormously increased their value. He often refused to build, although there was intense pressure for land and buildings. His policy was to wait until the time when those whom necessity drove to use his land should come to him as supplicants and accept his own terms. For a considerable time no one cared to take his land on lease at his onerous terms. But, finally, such was the growth of population and business, that his land was indispensable and it was taken on leaseholds. Astor's exactions for leaseholds were extraordinarily burdensome. But he would make no concessions. The lessee was required to erect his dwelling or business place at his own expense; and during the period of the twenty-one years of the lease, he not only had to pay rent in the form of giving over to Astor five or six per cent of the value of the land, but was responsible for all taxes, repairs and all other charges. When the ground lease expired the buildings became Astor's absolute property. The middleman landlord, speculative lessee or trading tenant who leased Astor's land and put up tenements or buildings, necessarily had to recoup himself for the high tribute that he had to pay to Astor. He did this either by charging the worker exorbitant rents or demanding excessive profits for his wares; in both of which cases the producers had finally to foot the bill. EVASION OF ASSESSMENTS BY THE LANDLORDS.