Foreigners remarked on the enormous quantities of art produced and the large fairs where many paintings were sold – it has been roughly estimated that over 1.3 million Dutch pictures were painted in the 20 years after 1640 alone. The volume of production meant that prices were fairly low, except for the best known artists; as in most subsequent periods, there was a steep price gradient for more fashionable artists. Those without a strong contemporary reputation, or who had fallen out of fashion, including many now considered among the greatest of the period, such as Vermeer, Frans Hals and Rembrandt in his last years, had considerable problems earning a living, and died poor; many artists had other jobs, or abandoned art entirely. In particular the French invasion of 1672 (the "Rampjaar", or "year of disaster"), brought a severe depression to the art market, which never quite returned to earlier heights.