Less than five percent of the nation's businesses account for the bulk of employment and revenue gains in the economy, according to a study by the Small Business Administration's Office of Advocacy.

Most of these so-called high-impact firms, which researchers defined as those that have doubled sales in the last four years, tended to be well-established smaller firms, having been in business for an average of 25 years. They were also less likely to be in the high-tech market, the study found.

"While high-impact firms make up about five percent of firms with employees, their effects are huge," Brian Headd, an agency economist, said in a statement.

Located across of the country, high-impact firms outpaced others in job growth, with job losses coming predominantly from large low-impact firms, the study found