* Shutdown enters fourth day, investors watch debt ceiling
* Dow, S&P 500 on track for second straight week of losses
* Adobe Systems down; hackers stole source code, client data
* Indexes: Dow down 0.1 pct, S&P flat, Nasdaq up 0.1 pct
By Ryan Vlastelica
NEW YORK, Oct 4 (Reuters) - U.S. stocks were little changedon Friday, with major indexes on track for a week of steeplosses amid concerns about a partial shutdown of the U.S.government which entered a fourth day.
The S&P 500 has fallen for nine of the past 11sessions, with the losses driven by a budget stalemate inCongress that has closed the government since midnight Monday.At the center of the impasse was the Affordable Care Act, dubbedObamaCare, a heathcare reform plan signed into law by PresidentBarack Obama in 2010.
The shutdown appeared likely to drag on for another week ormore, with little sign of progress towards a solution. Investorsare also watching the situation for how the upcoming debate overthe debt ceiling might play out.
"People are reasonably sure Congress will reach an agreementto both reopen the government and raise the debt ceiling beforethe debt-ceiling deadline. Markets are pretty calm in the faceof that belief, correctly reflecting the lack of any real harmso far," said Kate Warne, investment strategist at Edward Jonesin St. Louis.
While a short-term closure was expected to have a modesteconomic impact, the effect is expected to become morepronounced the longer it lasts.
Dennis Lockhart, president of the Federal Reserve Bank ofAtlanta, said the shutdown would hurt growth in the last quarterof this year, while the Bank of Japan said an extended budgetstandoff would have a severe global impact.
The debt ceiling issue is considered more severe as it couldresult in a default on U.S. debt if no resolution is reached toincrease it. On Thursday, the New York Times reported that HouseSpeaker John Boehner told colleagues he would not let the UnitedStates default on its debt.
"If there's no agreement by the end of next week, theconcern will really become greater and the impact will be morepronounced," said Warne, who helps oversee $670 billion inassets.
The Dow Jones industrial average was down 16.70points, or 0.11 percent, at 14,979.78. The Standard & Poor's 500Index was down 0.58 points, or 0.03 percent, at 1,678.08.The Nasdaq Composite Index was up 2.91 points, or 0.08percent, at 3,777.26.
While shutdown concerns have pressured equities over thepast two weeks, the S&P 500 index has frequently foundsupport at its 50-day moving average of 1,679.61, though itclosed slightly below that level on Thursday.
For the week, the Dow is down 1.8 percent and the S&P hasslipped 0.8 percent for a second week of losses for bothindexes, while the Nasdaq has shed 0.1 percent.
The CBOE Volatility Index, a measure of investoranxiety, is up 36 percent over the past two weeks, the biggesttwo-week jump for the index since September 2011.
Government economic data has been delayed because of theshutdown, and the September payroll report was not released asscheduled. About 180,000 jobs were expected to have been addedin September, up from 169,000 added in the previous month.
Adobe Systems Inc fell 0.6 percent to $50.56, a dayafter the company said hackers had stolen source code to some ofits most popular software as well as the confidentialinformation of millions of its customers.
Union Pacific Corp gave a third-quarter earningsoutlook late Thursday that was below expectations, as floodingin Colorado weighed on coal shipments. Shares fell 1.1 percentto $153.75.
Twitter Inc gave potential investors their first glance atits financials on Thursday when it publicly filed documents foran initial public offering. The information showed that revenueat the social networking company almost tripled in 2012, thoughit posted a loss in the first half of 2013.
Potbelly Corp said late Thursday its initial publicoffering of 7.5 million shares had priced at $14 each.
- Investment & Company Information