The Department of State’s Visa Bulletin for February 2019 notes the following concerning employment-based immigrant visa number availability on a monthly basis through May:
EMPLOYMENT-based categories (potential monthly movement)
WORLDWIDE (most countries): Up to two months.
China and India: Up to one month.
Worldwide: Current for the foreseeable future.
China: Up to three months.
India: Up to one week
China: Up to three weeks.
India: Up to three months.
Philippines: Rapid movement to generate demand.
Employment Fourth: Current for most countries.
El Salvador, Guatemala, and Honduras: Up to one week.
Mexico: Rapid forward movement until limit is reached.
Employment Fifth: The category will remain “Current” for most countries.
China-mainland born: Up to one week.
Vietnam: Up to three weeks.
The above final action date projections indicate what is likely to happen on a monthly basis through May. The determination of the actual monthly final action dates is subject to fluctuations in applicant demand and a number of other variables. It is also important to remember that by no means has every applicant with a priority date earlier than a prevailing final action date been processed for final visa action, with applicants often processing at their own initiative and convenience.