By Michael Santoli

The Dow Jones Industrial Average jumped above 15,000 for the first time in its long history Friday morning on the strength of a thousand fears going unrealized.

The employment report for April — showing a greater-than-forecast 165,000 new jobs and an unemployment rate slipping down to 7.5% — was just the latest bit of economic news that looked merely OK but was good enough to allay widespread anxiety that the U.S. economic recovery was buckling.

Traders were clearly leaning in the direction of a weaker result following a subpar estimate of April private-sector job gains by ADP on Wednesday. This has been the abiding pattern of the 2013 rally – a steep wall of worry about government- spending cuts, weak corporate revenue growth, tax increases and sluggish overseas economies that is scaled with the help of strong corporate balance sheets, sturdy credit markets, cheap money furnished by central banks and investors’ replenished risk appetite.

Splashy round index levels — which now include the Standard & Poor’s 500 above 1,600 for the first time — often lead the market to stall out for a while, and the rally since mid-November is among the longest ever without at least a 5% pullback. So a sideways slide or a dip would make a lot of sense.

Yet there’s also the possibility that the widely sounded “Sell in May” cry has become so loud that such a downturn has been over-anticipated by investors.

“This is the same rally we’ve had forever,” says Breakout’s Jeff Macke in the attached video. “We’re due for a pause, the data’s not that great – just shut up and stay long.” The encouraging action suggests a grudging acknowledgement that the economy is good enough and alternatives unattractive enough for “up” to be the default direction of the market trend, until proven otherwise.

Macke continues, “The economy’s slowly improving, earnings are OK, there’s nowhere else to go and – You know what? – sometimes a bullish market is just a bullish market.”

Stocks have benefited mightily from a ferociously strong corporate-debt market, which in turn has enjoyed the gift of zero-percent official interest rates and massive demand for safe cash yields. Companies' ability to borrow at historically cheap rates and buy back stock or pay dividends with cheap capital has been a huge driver of the upside. Apple Inc.’s (AAPL) stunning $17 billion bond sale to fund its enhanced dividend-and-buyback plan pointed to the relative attractiveness of equities with cash flow levels broadly exceeding their cost of debt.

The key question at this point, with the S&P 500 up more than 13% year to date, is whether more-traditional economically cyclical sectors can begin pulling their weight. The upside so far in 2013 has been led by more “defensive,” bond-like stocks in the utilities, telecommunications, consumer-staples and pharmaceutical industries.