[cem] Specifying Breaks for L1 Measure

I am trying to understand why the imbalance command produces a univariate L1 measurement of 0 on a variable (readscore6) that has significant imbalance (ctl mean = 83.9, trt mean = 76.0, ttest p<.001, standardized mean difference from MatchIt = -1.5385). I figure this must be because of the automatic breakpoints, so I examine how the univariate L1 measure changes using the L1.profile command (dropping all other variables). The L1 reportedly varies from 0 to 0.59 in the sets of cutpoints examined. I replicate 3 of these L1 measurements precisely "by hand" and they seem correct. But when I add breaks to the imbalance command, I cannot replicate the L1 values produced in L1.profile. Any idea what is going on here? Thanks in advance for any insights. Additional details follow: Univariate L1 is 0, even though multivariate L1 is 0.563 and imbalance test is restricted to single variable "readscore6": Multivariate Imbalance Measure: L1=0.563 Percentage of local common support: LCS=57.1% Univariate Imbalance Measures: statistic type L1 min 25% 50% 75% max readscore6 -16.45865 (diff) 0 -21 -18 -19 -21 -11 L1 varies between 0 and 0.59 in a small sample of sets of cutpoints: rnd(4) rnd(3) rnd(5) rnd(1) rnd(2) 0.0000000 0.4601504 0.4969925 0.5631579 0.5872180 $`rnd(4)` $`rnd(4)`$readscore6 [1] 38 97 $`rnd(3)` $`rnd(3)`$readscore6 [1] 38.00 52.75 67.50 82.25 97.00 $`rnd(5)` $`rnd(5)`$readscore6 [1] 38.00000 57.66667 77.33333 97.00000 $`rnd(1)` $`rnd(1)`$readscore6 [1] 38.00000 44.55556 51.11111 57.66667 64.22222 70.77778 77.33333 83.88889 90.44444 97.00000 $`rnd(2)` $`rnd(2)`$readscore6 [1] 38.000 45.375 52.750 60.125 67.500 74.875 82.250 89.625 97.000 Cannot seem to replicate these L1 values in the imbalance command, specifying the same cutpoints: E.g. specifying 2 cutpoints (1 bin) produces L1 of 0.563 (should be 0 according to L1.profile as well as my understanding of how L1 is calculated) Multivariate Imbalance Measure: L1=0.563 Percentage of local common support: LCS=57.1% Univariate Imbalance Measures: statistic type L1 min 25% 50% 75% max readscore6 -16.45865 (diff) 0.5631579 -21 -18 -19 -21 -11 E.g. specifying 5 cutpoints (4 bins) produces L1 of 0.563 (should be 0.46 according to L1.profile) Multivariate Imbalance Measure: L1=0.563 Percentage of local common support: LCS=57.1% Univariate Imbalance Measures: statistic type L1 min 25% 50% 75% max readscore6 -16.45865 (diff) 0.5631579 -21 -18 -19 -21 -11 Bridget Lavelle, Ph.D. Senior Research Manager Program Research and Evaluation Section Research and Data Analysis Division Department of Social and Health Services PO Box 45204 Olympia, WA 98504-5204 Fax: (360) 902-0705 Email: Bridget.Lavelle@dshs.wa.gov<mailto:Bridget.Lavelle@dshs.wa.gov> Telephone: (360) 902-0741