When you think of high tech start-ups, you probably think of the businesses that have become household names. You don't hear very much about businesses that failed, or of the people who developed great inventions but weren't able to build successful companies with them.

The numbers are daunting; according to John Nesheim, author of "High Tech Start Up: The Complete Handbook for Creating Successful New High Tech Companies," anyone considering starting a business should ponder these statistics:

1. The chances are six in a million that an idea for a high-tech business eventually becomes a successful company that goes public.

2. On the average, a venture capitalist finances only six out of every 1,000 business plans received each year.

3. Bankruptcies occur for 60 percent of the high-tech startup companies that succeed in getting venture capital.

4. Mergers or liquidations occur in 30 percent of start-up companies.

According to the Small Business Administration, only about half of new employer firms survive four years or more; business survival varies by industry and demographics. The industry with the highest 1992-1996 survival rate for firms owned by white non-Hispanics was oil and gas extraction (82 percent survival rate over the four-year period). African Americans were most successful in legal services (79 percent), and Hispanic and Asian Americans in health services (66 percent and 76 percent, respectively).

The SBA reports 572,900 new firms and 584,800 closures (both about 10 percent of the total) in 2003.

Starts and Closures of Employer Firms, 1995-2003

Sources: U.S. Bureau of the Census; Administrative Office of the U.S. Courts; U.S. Department of Labor, Employment and Training Administration.

If you don't find these statistics daunting, then you might have one of the key qualities of a successful entrepreneur: tenaciousness. Vinod Khosla, founding chief executive officer of Sun Microsystems, tried starting up his first company in India and failed, then was rejected by Stanford Business School twice before he "yelled and screamed" his way into the school.

"First lesson: don't give up," Khosla told a group of students at Stanford University. "Evangelism is really important when you're trying to get something done." (Click here to listen to Khosla's remarks.)

Khosla's experience with a failed start-up is typical; many successful entrepreneurs, including R.H. Macy, H.J. Heinz, and George Westinghouse have started up duds. A 1994 analysis of Inc. magazine's top 500 companies found that half the entrepreneurs who earned a spot on the list had started other businesses, of which one third had died untimely deaths.

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