Keep in mind scarcity depends on the market a property resides in, though, so demand tends to vary.
Supply and demand imbalances are an example of external factors. For example, if your property is located in an area experiencing a booming economy and increasing population, it will likely appreciate. Real estate is a scarce asset. More raw land can’t be created, which leads to an increase in demand as scarcity increases. Keep in mind scarcity depends on the market a property resides in, though, so demand tends to vary.