As the U.S. markets take a break for the long Independence Day weekend, economic worries and a disastrous June on the markets are battering shares of high-fliers including Apple, Google and Amazon, underscoring concerns about tech-sector growth.

The tech-heavy Nasdaq closed the first half this week at 2292, down from its 2609 opening in January. IT bellwethers raked in better-than-expected and, in some cases, record sales and profits so far this year. But anxiety about rising energy prices, consumer spending and the credit-market turmoil have also caused IT investors to worry.

As fears of a recession hit the U.S. in January, the Nasdaq took a nosedive. After a raft of good first-quarter financials from the likes of Apple, Google, AT&T and IBM, among others, tech-vendor shares seemed on the upswing after a March low -- until oil prices starting shooting up and inflation fears started to get into the mix of economic news. These concerns climaxed over the past few weeks, resulting in the worst June on the stock market since 1930.

Most of the stocks that drove last year's strong performance, in earnings and in share prices, are down for the first half.

For example, Apple, Google, Amazon and Research In Motion contributed to more than 60 percent of the Nasdaq's gain last year, according to brokerage Sanford C. Bernstein. That in itself calls into question whether confidence in IT last year was all that robust. But it's worse this year: Of those top four IT stocks only RIM is up, closing at US$116.90, up $3.19 from its opening price in January.

It's bad news for the rest: Apple closed the first half at $167.44, down by $27.40; Google closed at $526.42, down by $158.77; and Amazon closed at $73.33, down by $22.92.

Still, just about every week, there is good news about the underlying vitality of the sector. This week the Semiconductor Industry Association said global chip sales grew 7.5 percent in May, defying predictions that economic issues would put a damper on the market.

And despite the credit-market crisis, money is pouring into fuel R&D in hot topics. For example, the 451 Group this week reported that venture capital funding for open source rose in the second quarter compared to last year, by 14 percent to $115.5 million.

The IDG News Service is a Network World affiliate.