The Dow closed yesterday at 13,358.31; ten years before, it stood at 8,254.89. That's a compound annual growth rate of 4.93% (less, when you adjust for inflation).
Or if you take it from the big, big scare of Monday 19 October 1987 (close: 1,738.74, down 508 points from the previous Friday!), it's an average 10.88% compound per year. Does that seem too hot a pace? Unsustainable? But remember that we're starting that run from a real panic. If we took it from the happy close of the Friday before, the average becomes 9.53%.
Still too hot? If nearly 20 years isn't enough to establish a sensible long-term trend, let's look at an even longer period: 30 years from 30 July 1977. Then till now, the Dow's capital growth averages out at 9.45% compound per year. The market's folly can outlast your wisdom.
"Two views make a market", and that's it. Mr Market is making his wares available to you - will you buy at today's prices? (I wouldn't - but obviously others will, or the market would be lower.)
You can play with the figures yourself, on this fine page from Yahoo! Finance.
And please click on the poll opposite, to give your prediction for the year's end.