Comparison between the density of sources observed at 3 ≤ z ≤ 7 behind A1689 and expectations based on the extrapolation of the LF toward the low-luminosity regime covered by the present survey. References are given in the figure for different redshifts. Solid lines display the steepest slopes adopted for the LF fit: α = −1.7 for Kashikawa et al. (2011) and Blanc et al. (2011), α = −2.0 for Shioya et al. (2009), and α = −1.6 for Dawson et al. (2007). Dashed and dotted lines correspond to α = −1.5 and −1.3 for Kashikawa et al. (2011) and α = −1.5 and −1.0 for Shioya et al. (2009). Error bars include Poisson noise statistics and field-to-field variance (see text).