i put to gether the table and data, but didn't have time to continue; this might help in the analysis:
create table #SpreadSheet(
Zip varchar(9),
City varchar(60),
County varchar(60),
State varchar(2),
CntDef char(1),
Ddef char(1),
CombSTax decimal(10,4),
CombUTax decimal(10,4),
EffectiveDate datetime )
INSERT INTO #SpreadSheet VALUES ('90001','FIRESTONE PARK ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('90001','FIRESTONE PK ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('90001','LOS ANGELES ','LOS ANGELES ','CA',' ','Y',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('90001','FIRESTONE PARK ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2005')
INSERT INTO #SpreadSheet VALUES ('90001','FIRESTONE PK ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2005')
INSERT INTO #SpreadSheet VALUES ('90001','LOS ANGELES ','LOS ANGELES ','CA',' ','Y',0.0825,0.0825,'1/1/2005')
INSERT INTO #SpreadSheet VALUES ('90002','AUGUST F. HAW ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('90002','LOS ANGELES ','LOS ANGELES ','CA',' ','Y',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('90002','WATTS ','LOS ANGELES ','CA',' ',' ',0.0825,0.0825,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('96161','NORTHSTAR ','NEVADA ','CA',' ',' ',0.07375,0.07375,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('96161','TRUCKEE ','NEVADA ','CA','Y','Y',0.07875,0.07875,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('96161','TRUCKEE ','PLACER ','CA',' ',' ',0.0725,0.0725,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('96162','TRUCKEE ','NEVADA ','CA',' ',' ',0.07875,0.07875,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('95526','BRIDGEVILLE ','HUMBOLDT ','CA',' ','Y',0.0725,0.0725,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('95526','RUTH ','HUMBOLDT ','CA',' ',' ',0.0725,0.0725,'1/1/2002')
INSERT INTO #SpreadSheet VALUES ('95526','RUTH ','TRINITY ','CA','Y',' ',0.0725,0.0725,'1/1/2002')
Lowell