Give the main reason for decline of Spain’s power.

The decline of Spain's power in the late 16th and 17th centuries can be attributed to a combination of factors, but a main reason for this decline was the economic problems that the country faced. Spain's economy, heavily reliant on the wealth extracted from its colonies, was unsustainable. The influx of silver and gold from the New World initially made Spain incredibly wealthy, but this wealth was not managed well. Spain used this wealth to fund costly wars across Europe to defend the Catholic faith and expand its territories, which led to immense military expenditures.

Moreover, inflation, or the 'Price Revolution,' was another significant issue. As silver and gold flooded into Europe from the Americas, it led to a sharp increase in prices due to the debasement of currency and the increase in the money supply. Spain's economy was also not diversified enough, heavily dependent on agriculture and not as engaged in commerce or industry as other growing European powers. This made Spain less competitive in the global economic scene.

The constant warfare, along with neglect of domestic development, excessive taxation, and failure to invest in productive enterprises, led to Spain's economic base being eroded. This economic deterioration weakened Spain's ability to maintain its dominance over its European rivals and its vast global empire, resulting in the decline of its power.