What was one major effect of De Beers' control over diamond production?

De Beers' control over diamond production had a significant impact on the diamond market, one of the most notable effects being the stabilization of diamond prices. By carefully managing the supply of diamonds, De Beers was able to create an environment where prices did not fluctuate wildly based on demand. They implemented a strategy of stockpiling and releasing diamonds onto the market in controlled quantities, which effectively prevented oversupply that could lead to price drops. This manipulation of supply allowed them to maintain consistent pricing, making diamonds appear rare and desirable, which further entrenched their value in the consumer market.

In contrast to this, other options like increased competition among miners or expansion of diamond mining areas did not occur prominently due to De Beers' strong market influence, which often resulted in the opposite of those conditions. Additionally, maintaining quality was a key aspect of their strategy, so the reduction in diamond quality does not align with the practices that De Beers was known for historically.