diff --git a/README-alt.md b/README-alt.md
index e05a225..14c5d58 100644
--- a/README-alt.md
+++ b/README-alt.md
@@ -135,6 +135,31 @@ other programs for typing such as [Warren et al (2012)][hla4], [Liu et al
 (2013)][hla2], [Bai et al (2014)][hla3] and [Dilthey et al (2014)][hla1], though
 most of them are distributed under restrictive licenses.
 
+## Preliminary Evaluation
+
+To check whether GRCh38 is better than GRCh37, we mapped the CHM1 and NA12878
+unitigs to GRCh37 primary (hs37), GRCh38 primary (hs38) and GRCh38+ALT+decoy
+(hs38d6), and called small variants from the alignment. CHM1 is haploid.
+Ideally, heterozygous calls are false positives (FP). NA12878 is diploid. The
+true positive (TP) heterozygous calls from NA12878 are approximately equal
+to the difference between NA12878 and CHM1 heterozygous calls. A better assembly
+should yield higher TP and lower FP. The following table shows the numbers for
+these assemblies:
+
+|Assembly|hs37   |hs38   |hs38d6|CHM1_1.1|  huref|
+|:------:|------:|------:|------:|------:|------:|
+|FP      | 255706| 168068| 142516|307172 | 575634|
+|TP      |2142260|2163113|2150844|2167235|2137053|
+
+With this measurement, hs38 is clearly better than hs37. Genome hs38d6 reduces
+FP by ~25k but also reduces TP by ~12k. We manually inspected variants called
+from hs38 only and found the majority of them are associated with excessive read
+depth, clustered variants or weak alignment. We believe most hs38-only calls are
+problematic. In addition, if we compare two NA12878 replicates from HiSeq X10
+with nearly identical library construction, the difference is ~140k, an order
+of magnitude higher than the difference between hs38 and hs38d6. ALT contigs,
+decoy and HLA genes in hs38d6 improve variant calling at little cost.
+
 ## Problems and Future Development
 
 There are some uncertainties about ALT mappings - we are not sure whether they
diff --git a/extras/alt-demo.graffle b/extras/alt-demo.graffle
index ff47a30..32a8f5f 100644
--- a/extras/alt-demo.graffle
+++ b/extras/alt-demo.graffle
@@ -104,17 +104,17 @@
 
 \f0\fs24 \cf2       Read: A\cf0 TCAGCATC\
 \cf2 \
- ALT ctg 1:       \cf3  TGA\cf3 AA---CGAATGCAAATCA
+ ALT ctg 1:       \cf3  TGA\cf3 AA---CGAATGCAAATGGTCA
 \f1\b \cf4 ATCAGCATC
 \f0\b0 \cf3 GAACTAGTCACAT\cf2 \
-           \cf3         |||||\cf5  (high div) \cf3 |||\cf5  (novel ins)\cf3  ||||||||||\cf2 \
+           \cf3         |||||\cf5  (high div) \cf3 ||||||\cf5  (novel ins)\cf3  ||||||||||\cf2 \
 Chromosome:\cf3  GCGTACATGATACGA
 \f1\b \cf6 ATCgGCATC
-\f0\b0 \cf3 ATC-------------CTAGTCACATCGTAATCGA\
-\cf2            \cf3         |||||||||||| |||||||\cf5  (novel ins) \cf3 ||||||||||\
+\f0\b0 \cf3 ATGGTC-------------CTAGTCACATCGTAATC\
+\cf2            \cf3         |||||||||||| ||||||||||\cf5  (novel ins) \cf3 ||||||||||\
 \cf2  ALT ctg 2:\cf3         TGATACGA
 \f1\b \cf7 ATCgcCATC
-\f0\b0 \cf3 ATCA
+\f0\b0 \cf3 ATGGTCA
 \f1\b \cf8 ATCgcCAgC
 \f0\b0 \cf3 GAACTAGTCACAT\
 \
@@ -140,7 +140,9 @@ Chromosome:\cf3  GCGTACATGATACGA
 \cf0 Hits considered in mapQ: 
 \f1\b \cf4 ATCAGCATC
 \f0\b0 \cf0  and 
-\f1\b \cf6 ATCgGCATC\
+\f1\b \cf6 ATCgGCATC
+\f0\b0 \cf2  (best from each group)
+\f1\b \cf6 \
 \pard\tx560\tx1120\tx1680\tx2240\tx2800\tx3360\tx3920\tx4480\tx5040\tx5600\tx6160\tx6720\pardirnatural
 
 \f0\b0 \cf3 \
@@ -217,7 +219,7 @@ Chromosome:\cf3  GCGTACATGATACGA
 	<key>MasterSheets</key>
 	<array/>
 	<key>ModificationDate</key>
-	<string>2014-11-17 18:01:49 +0000</string>
+	<string>2014-11-17 18:28:10 +0000</string>
 	<key>Modifier</key>
 	<string>Heng Li</string>
 	<key>NotesVisible</key>
diff --git a/extras/alt-demo.png b/extras/alt-demo.png
index efd247c..71f4976 100644
Binary files a/extras/alt-demo.png and b/extras/alt-demo.png differ