Although a couple of dictionaries I have checked give 'negoziante/fornitore' come traducente, I know that plumbers, carpenters, electricians and similar are also referred to as 'Tradesmen'. I found several websites that use this terminology, I post one below.

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Note added at 20 mins (2010-08-20 09:01:38 GMT)
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This if you are just referring to plumbers, carpenters, etc, of course.

"la proporzione di lavoratori autonomi, quasi esclusivamente lavoratori in proprio, risulta tra gli uomini più elevata che tra le donne"

The proportion of self-employed workers (who are individuals) working almost exclusively on their own (account) is higher among men than women.


http://shortify.com/10928


http://shortify.com/10929

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Note added at 1 hr (2010-08-20 09:57:28 GMT)
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An afterthought:

How about "<v>freelance workers" ?

Self-employed workers include independent contractors, freelance workers and those who own their own unincorporated businesses.
http://shortify.com/10930





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Note added at 1 hr (2010-08-20 09:58:48 GMT)
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Correction of typo:

How about "<v>freelance workers" ? --> How about "freelance workers" ?



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Note added at 1 hr (2010-08-20 10:00:09 GMT)
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lavoro in proprio freelance work
lavoratori in proprio freelance workers

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Note added at 1 hr (2010-08-20 10:10:32 GMT)
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In that case, your sentence would read:
The proportion of self-employed workers (who are individuals) working almost exclusively as freelancers is higher among men than women.

... self employed workers, almost exclusively "free lancers" in the sense that while they have no employers, they are not employers themselves,...

I've never heard of this distinction before and I am a "lavatore autonomo" who has been working "in proprio" for years. The only translation that will work is one that contains an explanation, just of course as IMHO the Italian needs an explanation, if anybody is to understand it. Perhaps I am wrong.


http://www.provincia.bergamo.it/ProvBgSettori/provBgSettoriH...
Liberi professionisti

Coloro che eserecitano *** in proprio *** una professione o un'arte liberale (notai, medici, avvocati, commercialisti...), caratterizzata da attività prevalentemente intellettuali.

A notaio without an employee must be a rare specimen.

This term is very common, while "sole trader" is not.

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Note added at 10 hrs (2010-08-20 19:07:10 GMT)
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Of course this would be for "lavoratore"

Self-employment is working for one's self rather than for another person or company. In other sense, it is, earning one's livelihood directly from one's own trade or business rather than as an employee of another. To be self-employed, an individual is normally highly skilled in a trade or has a niche product or service for his or her local community.

http://en.wikipedia.org/wiki/Self-employment

-A sole proprietorship is a business which has only one owner. It is a "sole" proprietor in the sense that the owner has no partners. A sole proprietorship essentially means a person does business in his own name and there is only one owner. A sole proprietorship is not a corporation, it does not pay corporate taxes, but rather the person who organized the business pays personal income taxes on the profits, making accounting much simpler.
A sole proprietorship has an authority to hire any number of employees because the law makes no distinction between you, the sole proprietor, and the business. Sole proprietorship has also an authority to hire independent contractors of their own choice.
Whether the proprietor has zero or 100 employees or independent contractors, it doesn't make any difference. If you are the sole owner, your business will still be a sole proprietorship-