National Interest Waiver. This refers to the fact that it must be in the national interest to waive the labor certification for the applicant in order to be approved in this category.
No. It is an Employment-based 2nd preference category. For most individuals, this does not affect immigrant visa availability. However, nationals of China and India have a longer waiting period due to high demand. See the Visa Bulletin for details.
This is a somewhat subjective criterion, but often the key to the National Interest Waiver petition is letters or recommendation from peers in the individual's field of expertise. In addition to the proposed future benefits of the individual's work, he or she must have already made significant contributions to their field. This is reflected in the letters, as well as in publications by or about the individual, awards, grants, or other materials relevant to the field.
An NIW does not need to be empoyer-sponsored, but it is an option. Some practitioners believe that an employer-sponsored petition can help make the application stand out, but there is no concrete evidence of this.
Apart from sending us your documents and telling us about your area of expertise, there are a few things you can do to increase your likelihood of success, particularly if you are a researcher/academic.See a list of resources here.
Processing times for a "National Interest Waiver" varies from year to year, from a few months to a couple of years. NIW petitions are not eligible for Premium Processing. The USCIS posts its current processing times on their website.
The next step is to file for permanent residence based on the approved I-140 in the U.S. or at a U.S. consulate abroad. The permanent residence application may also be filed concurrently with the I-140 National Interest Waiver, depending on the availability of immigrant visa numbers in the employment-based second preference category of the Visa Bulletin.