Reportedly is an adverb describing the action of reporting something that someone else told you, and there is no absolute way to verify it. Reportedly is often (but not always) used to discuss crimes and motives for wrong doing. People don't use it much in everyday conversations with friends, etc. In normal conversation, a similar, but more common word to use in conversation would be supposedly. Supposedly refers to things that one supposes to be true, rather than a more official "report" of what is true. An example: "The boy went to the market reportedly to buy tomatoes; so it seems odd that he never arrived to the store." "Supposedly, the boy was going to the store to buy tomatoes-- so it seems odd that he never arrived." The first example (using reportedly) is more what you would find in a newspaper, or that people would use to discuss a case, a crime, or a strange occurrence. The second example (using supposedly) is more what you would find in conversation.

Here is the Google definition: Reportedly (adverb): according to what some say (used to express the speaker's belief that the information given is not necessarily true "He was last spotted in China, reportedly to discuss his company's new project." This adverb is seen fairly commonly in print, like a news magazine, but not often in spoken conversation.

Reportedly is used mostly in writing and perhaps more formal talks/speeches. But me personally, I would say "supposedly" when I talk. Like Daniel said, your example isn't too natural. Here's a better example: Riots have been reportedly taken place in London. This actress reportedly had an affair with her manager. Does this make sense?

Your example is not very good, because oil prices are simple facts, easy to verify. If you were not 100% sure it is correct, mention the source for your information: "The Wall Street Journal REPORTS that oil prices have risen for the past three weeks."

Daniel, Samuel and Jetta, Thank you for your reply with detailed explanations. All of your comments helped me to understand this adverb. Also I have known of the adverb "supposedly" for the first time. Have a wonderful week.