The American Immigration Lawyers Association reported  11th that they received the following information concerning the availability of visa numbers:

The surge in usage of the employment-based fourth and fifth preference numbers is significant beyond those specific categories themselves because, historically, there have been substantial unused numbers in these categories which have been used to meet demand for visas in the employment-based first and second preference categories, allowing the China and India cut-off dates to advance further than would be possible if those categories are limited to only their annual limits. This means EB2 immigrants from China and India could have an even longer wait to obtain green cards.