当产品被政府制成非法时，通常会出现针对该产品的黑市。但是，当货物从合法市场转向黑市时，供需如何变化？简单的供需图可以证明有助于可视化这种情况。让我们看看黑市如何影响典型的供需图表，以及这对消费者意味着什么。要了解当商品被非法化时会发生什么变化，首先要说明在黑市前的日子里，商品的供需情况是什么样的。为此，任意绘制向下倾斜的需求曲线（以蓝色显示）和向上倾斜的供应曲线（以红色显示），如此图所示。请注意，价格在X轴上，数量在Y轴上。 2条曲线之间的交点是当商品合法时的自然市场价格。当政府将产品定为非法时，随后会形成黑市。当政府制造非法产品（如大麻）时，往往会发生两件事。首先，供应量急剧下降，因为销售商品的罚款导致人们转向其他行业。其次，观察到需求下降是为了禁止某些消费者想要购买它。供应量下降意味着向上倾斜的供应曲线将向左移动。同样，需求下降意味着向下倾斜的需求曲线将向左移动。通常，当政府创造黑市时，供给副作用主导需求方。意思是，供给曲线的变化大于需求曲线的变化。此图显示了新的深蓝色需求曲线和此图中新的暗红色供应曲线。现在，看看新的供需曲线相交的新点。供需变化导致黑市的消费量减少，而价格上涨。如果需求副作用占主导地位，消费量将会下降，但价格也会相应下降。然而，这通常不会发生在黑市中。相反，价格通常会上涨。价格变化的数量和消费量的变化将取决于曲线变化的幅度，以及需求的价格弹性和供应的价格弹性。
英国诺丁汉大学经济论文代写：消费量
When a product is made illegal by the government, a black market for the product usually appears. But how does supply and demand change as goods move from a legitimate market to a black market? A simple supply and demand map can prove helpful in visualizing this situation. Let’s see how the black market affects typical supply and demand charts and what this means for consumers. To understand what happens when a commodity is illegal, first of all, what is the supply and demand situation of the commodity in the days before the black market. To do this, draw a downward-sloping demand curve (shown in blue) and an upward-tilted supply curve (shown in red), as shown in this figure. Note that the price is on the X-axis and the number is on the Y-axis. The intersection between the two curves is the natural market price when the goods are legal. When the government makes the product illegal, a black market will follow. When the government manufactures illegal products (such as marijuana), two things often happen. First, supply has fallen sharply because fines for selling goods have led people to switch to other industries. Second, the decline in demand was observed to prohibit certain consumers from wanting to buy it. A drop in supply means that the upwardly inclined supply curve will move to the left. Similarly, a drop in demand means that the downwardly inclined demand curve will move to the left. Usually, when the government creates a black market, supply side effects dominate the demand side. This means that the change in the supply curve is greater than the change in the demand curve. This figure shows the new dark blue demand curve and the new dark red supply curve in this figure. Now, take a look at the new points where the new supply and demand curve intersect. Changes in supply and demand led to a reduction in black market consumption and higher prices. If demand side effects dominate, consumption will fall, but prices will fall accordingly. However, this usually does not happen in the black market. Instead, prices usually rise. The amount of price change and the change in consumption will depend on the magnitude of the curve change, as well as the price elasticity of demand and the price elasticity of supply.