Kevin deYoung has an interesting piece here on numbers in church (people, not the OT book). It includes some helpful observations by Leslie Newbigin and concludes with these words by DeYoung:
We love to see more people loving Jesus and living in greater accordance to his commands, but we should not think church size, when judged by the only Judge that really matters, is a reliable measure of a church’s success or a pastor’s faithfulness.