What is the default installlevel for windows installer?

If you do not provide any install开发者_高级运维level argument to msiexec, what is the default value that the Windows Installer Framework assumes? My tests seem to indicate 1, but I can't find any documentation that corroborates this.

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If no value is specified, the install level defaults to 1.

http://msdn.microsoft.com/en-us/library/aa369536(VS.85).aspx