Industry associations are a key source of statistics, trends, and other information. Although some associations will share key data only with members, many associations provide free information on their web sites. Industry information may also be found in periodicals published by associations (and these may be available in library databases).
Industry association web sites, publications, conferences, and association employees can be valuable sources of information.
Often an association is involved with legislative issues related to the industry and you can often find white papers on trade association sites that explain issues.
Some trade organizations gather valuable statistical and other information on the industry to produce useful publications. Although you can sometimes gather free info from the trade association site, often these publications are available only to members or are sold at high prices.
Sometimes you can gather good information through a phone call to a trade association--but sometimes they "won't give you the time of day." In rare cases, a large trade association may maintain a library--in those cases, the librarians at that library may be more willing to spend time giving you information than others at the organization.