Warren Buffett AP Images Warren Buffett is still bullish on the long-term outlook for US stocks.

The billionaire investor said he expects the index to be "over 1 million" in a hundred years, according to Reuters. He was speaking at an event celebrating the 100th anniversary of Forbes magazine.

He added that it's not an unreasonable forecast given the index was around 81 a hundred years back.

The Dow closed up by 0.18% at 22,370.80 on Tuesday.

Given that, it's worth noting that a value of 1,000,000 in 100 years translates into about a 4% compound annual growth rate, which is lower than the average rate stocks have historically grown.

Buffett's comments at the event reflect one of his long-standing beliefs: that over the long term, the stock market news will be good.

Back in October 2008, in the midst of the financial crisis, he explained that thinking in op-ed for The New York Times titled, "Buy American. I am.":

"Let me be clear on one point: I can’t predict the short-term movements of the stock market. I haven’t the faintest idea as to whether stocks will be higher or lower a month — or a year — from now. What is likely, however, is that the market will move higher, perhaps substantially so, well before either sentiment or the economy turns up. So if you wait for the robins, spring will be over. [...]

"Over the long term, the stock market news will be good. In the 20th century, the United States endured two world wars and other traumatic and expensive military conflicts; the Depression; a dozen or so recessions and financial panics; oil shocks; a flu epidemic; and the resignation of a disgraced president. Yet the Dow rose from 66 to 11,497."