When He broke the third seal, I heard the third living creature saying, "Come." I looked, and behold, a black horse; and he who sat on it had a pair of scales in his hand. And I heard something like a voice in the center of the four living creatures saying, "A quart of wheat for a denarius, and three quarts of barley for a denarius; but do not damage the oil and the wine." (Revelations 6:5-6 NASB)While it may not be evident to the modern reader, this much is established: the prices of the wheat and barley are absurdly expensive. If this was a merchant talking to a worker (earning one denarius a day), the worker would only be able to afford enough rice to feed himself that night, or enough barley to feed a family of three. Thus this produces the common interpretation of famine - that a lack of food has driven up prices to unsustainable levels. It is also of note that the oil and wine were not affected, either because these plants have deeper roots and so would be less susceptible to things like locust plagues, or because the society in the visions were overproducing oil and wine to suit their wealthy landlords (as the Roman Empire was doing at the time), and thus not producing adequate staple crops.
I think that famine is a very plausible explanation. But remember, this is merely one possible truth, and not a necessary truth. The verse does not specify that there is any shortage of wheat or barely; it merely states that the prices are high. So rather, the core of what the verse describes is price inflation, with no real explanation as to how or why.
Now, 'the horseman of inflation' probably does not sound quite as fearsome as 'the horseman of famine,' but its implications are far more chilling. Excessive inflation has had a silent but significant hand in many of human history's most horrific events. In fact, the earliest recorded inflation-induced destruction in Western history is none other than the fall of the Roman Empire itself, the very civilization that Jesus preached in. (At the time there was little theoretical understanding of economics, so Revelations would be truly prophetic!)
I believe the third horseman is not simply the horseman of famine or inflation, but the horseman of a broader malaise: unbridled, uncontrolled desire for economic gain - which in turn, produces symptoms such as famine or price inflation. What makes capitalism and its elements so insidious is that it is like cholesterol: a bit of it is not only good, it is necessary to keep the wheels of society turning. But like all things, these must be consumed in moderation. When a society sips upon the temptations for excessive capitalism, greed conquers the hearts of men, and the third horseman rides.