It has been pointed out to me that the 1903 gun law in England was rather weak,
and that real gun control started in 1920, so I have added a line to
the table below.
Second and third columns are homicide rate per 100,000 Year England & Wales USA Ratio Source 1903 0.93 2.6 1/3  1920 0.84 7.1 1/8  1988 0.6 9.0 1/15 
Over 85 years, there are lots of changes that that could affect
the homicide rate. Furthermore, the years 1903
and 1988 could be atypical and give a misleading picture. I made no
claim that this data proved that gun control was responsible for the
change. It was the original poster that claimed (based on incorrect
data) that a change in the opposite direction meant that gun control
To investigate the effects of the 1920 law we should compare the
homicide rate in England 1911-1920 to the rate 1921-1930, and also do
the same comparison for other nations (to see if, for example,
demographic changes caused by World War I caused the change.) My
source has data covering that period for Australia, England, Germany, Italy,
Japan, Netherlands, Portugal, Scotland, and the USA.