article comparing small entity and micro-entity status). The micro-entity provision of the law was effective as of September 16, 2011 but (according to the Federal Register) the new fees are not expected to be implemented until March 19, 2013 (about the same time the new first-to-file rules go into effect).
How do you determine micro-entity status for multiple inventors? The rules apply individually to each joint-inventor. So, no joint inventor can have been named as an inventor on more than four applications, and no joint inventor can have a gross income (as defined by the IRS) exceeding three times the median household income for the preceding calendar year (currently $150,162).