In a study of 2.7 million business, the proportion of companies with between three and 10 employees, with at least one female director rose from 48% to 50% between 2007 and 2012.
At companies with more than 250 workers, the figure rose from 33% to 40%.
Experian found that start-up businesses have also been important in bolstering the number of female directors employed.
One-third of the 1.4 million firms that started up since 2007 have one or more female director.
Max Firth, UK managing director for Experian's business information services division, said: "While there are undoubtedly many women who are breaking new ground and overcoming stereotypes, our data shows that among the total population of UK companies, the industries with most female directors are pretty much the same as before the recession."