Here's a very readable paper about the various efforts past, present, and future that are producing large scale systematic observations of millions of stars cataloging and categorizing the different types of variables, down to a variability of a few thousandths of a magnitude. The bulk of the article is about the Gaia mission, but it also covers Hipparchos, OGLE I & II, Pan-STARR, LSST, and others. Some of these surveys go down to 24th magnitude, and will enable rock solid statistical analysis in many new fields.
VARIABILITY ANALYSIS: DETECTION AND CLASSIFICATION