At the peak of tulip mania in Holland, in March 1637, some single tulip bulbs sold for more than 10 times the annual income of a skilled craftsman. It is generally considered the first recorded speculative bubble. The term "tulip mania" is now often used metaphorically to refer to any large economic bubble (when asset prices deviate from intrinsic values). The event was popularized in 1841 by British journalist Charles Mackay. According to Mackay, at one point 12 acres of land were offered for a Semper Augustus bulb. Mackay claims that many such investors were ruined by the fall in prices, and Dutch commerce suffered a severe shock. Some modern scholars, however, feel that the mania was not quite as extraordinary as Mackay described. Some even argue that not enough price data remain, historically, to represent an all out tulip bulb bubble. In her 2007 scholarly analysis Tulipmania, Anne Goldgar states that the phenomenon was limited to "a fairly small group", and that most accounts from the period are based on a few contemporary pieces of propaganda. While Mackay's account held that a wide array of society was involved in the tulip trade, Goldgar's study of archived contracts found that even at its peak the trade in tulips was conducted almost exclusively by merchants and skilled craftsmen who were wealthy, but not members of the nobility. Thus, any economic fallout from the bubble was very limited. Goldgar, who identified many prominent buyers and sellers in the market, found fewer than half a dozen who experienced financial troubles in the time period, and even of these cases it is not clear that tulips were to blame. This is not altogether surprising. Although prices had risen, money had not exchanged hands between buyers and sellers. Thus profits were never realized for sellers; unless sellers had made other purchases on credit in expectation of the profits, the collapse in prices did not cause anyone to lose money. There is no dispute that prices for tulip bulb contracts rose and then fell in 1636-37, but even a dramatic rise and fall in prices does not necessarily mean that an economic or speculative bubble developed and then burst. For tulip mania to have qualified as an economic bubble, the price of tulip bulbs would need to have become unhinged from the intrinsic value of the bulbs. Modern economists have advanced several possible reasons for why the rise and fall in prices may not have constituted a bubble. For one, the increases of the 1630s corresponded with a lull in the Thirty Years' War, which occurred between 1618 and 1648. Hence market prices were responding rationally to a rise in demand. However, the fall in prices was faster and more dramatic than the rise, and did not result from a sudden resurgence in the war.