Quarter	Number of Buildings
1960-01-01	9100
1960-04-01	18400
1960-07-01	22800
1960-10-01	21700
1961-01-01	11800
1961-04-01	19800
1961-07-01	21300
1961-10-01	23500
1962-01-01	13000
1962-04-01	24800
1962-07-01	26100
1962-10-01	28700
1963-01-01	8200
1963-04-01	23400
1963-07-01	26000
1963-10-01	29200
1964-01-01	11800
1964-04-01	30600
1964-07-01	31800
1964-10-01	22700
1965-01-01	15000
1965-04-01	23900
1965-07-01	21000
1965-10-01	33100
1966-01-01	12600
1966-04-01	20100
1966-07-01	22000
1966-10-01	39400
1967-01-01	14500
1967-04-01	31700
1967-07-01	32600
1967-10-01	21000
1968-01-01	19800
1968-04-01	30000
1968-07-01	32200
1968-10-01	25400
1969-01-01	20100
1969-04-01	29100
1969-07-01	31300
1969-10-01	25000
1970-01-01	18950
1970-04-01	23640
1970-07-01	20420
1970-10-01	25700
1971-01-01	16070
1971-04-01	26702
1971-07-01	26920
1971-10-01	34893
1972-01-01	16154
1972-04-01	25849
1972-07-01	24009
1972-10-01	32600
1973-01-01	16981
1973-04-01	19242
1973-07-01	20248
1973-10-01	23716
1974-01-01	13700
1974-04-01	18508
1974-07-01	15742
1974-10-01	33033
1975-01-01	8479
1975-04-01	11298
1975-07-01	12166
1975-10-01	19402
1976-01-01	10718
1976-04-01	16060
1976-07-01	13670
1976-10-01	16770
1977-01-01	9422
1977-04-01	13138
1977-07-01	12856
1977-10-01	18538
1978-01-01	11258
1978-04-01	14924
1978-07-01	14300
1978-10-01	16812
1979-01-01	10445
1979-04-01	15474
1979-07-01	13726
1979-10-01	16391
1980-01-01	10083
1980-04-01	12860
1980-07-01	12240
1980-10-01	14928
1981-01-01	8916
1981-04-01	10834
1981-07-01	11103
1981-10-01	13601
1982-01-01	8988
1982-04-01	10271
1982-07-01	10340
1982-10-01	12330
1983-01-01	8989
1983-04-01	9025
1983-07-01	8710
1983-10-01	11052
1984-01-01	6913
1984-04-01	8987
1984-07-01	7489
1984-10-01	10679
1985-01-01	7412
1985-04-01	6981
1985-07-01	6098
1985-10-01	7048
1986-01-01	5657
1986-04-01	7272
1986-07-01	7492
1986-10-01	10345
1987-01-01	7356
1987-04-01	8923
1987-07-01	9787
1987-10-01	13748
1988-01-01	11143
1988-04-01	12063
1988-07-01	12546
1988-10-01	15071
1989-01-01	13041
1989-04-01	15445
1989-07-01	14116
1989-10-01	16277
1990-01-01	15286
1990-04-01	16784
1990-07-01	16622
1990-10-01	20934
1991-01-01	14374
1991-04-01	14748
1991-07-01	13191
1991-10-01	14542
1992-01-01	10743
1992-04-01	16270
1992-07-01	5605
1992-10-01	16845
1993-01-01	3629
1993-04-01	2058
1993-07-01	1609
1993-10-01	4615
1994-01-01	1817
1994-04-01	2736
1994-07-01	2582
1994-10-01	4725
1995-01-01	2236
1995-04-01	2130
1995-07-01	2760
1995-10-01	5609
1996-01-01	2964
1996-04-01	3631
1996-07-01	2952
1996-10-01	3210
1997-01-01	1531
1997-04-01	2872
1997-07-01	2799
1997-10-01	4770
1998-01-01	2114
1998-04-01	3134
1998-07-01	2371
1998-10-01	5012
1999-01-01	2795
1999-04-01	3629
1999-07-01	3858
1999-10-01	4287
2000-01-01	3282
2000-04-01	4991
2000-07-01	3787
2000-10-01	4763
2001-01-01	4113
2001-04-01	4960
2001-07-01	5675
2001-10-01	4653
2002-01-01	4837
2002-04-01	5390
2002-07-01	4117
2002-10-01	4707
2003-01-01	4786
2003-04-01	5757
2003-07-01	4689
2003-10-01	6820
2004-01-01	6117
2004-04-01	7860
2004-07-01	5586
2004-10-01	7756
2005-01-01	7358
2005-04-01	9001
2005-07-01	6346
2005-10-01	9082
2006-01-01	7675
2006-04-01	9568
2006-07-01	8674
2006-10-01	19347
2007-01-01	6779
2007-04-01	6660
2007-07-01	6666
2007-10-01	7465
2008-01-01	6107
2008-04-01	5836
2008-07-01	4007
2008-10-01	5265
2009-01-01	3845
2009-04-01	4607
2009-07-01	4057
2009-10-01	5461
2010-01-01	5621
2010-04-01	8343
2010-07-01	5595
2010-10-01	7992
2011-01-01	8018
2011-04-01	8249
2011-07-01	4960
2011-10-01	5502
2012-01-01	5582
2012-04-01	6215
2012-07-01	4406
2012-10-01	5118
2013-01-01	7353
2013-04-01	7816
2013-07-01	6516
2013-10-01	8829
2014-01-01	8726
2014-04-01	9227
2014-07-01	7761
2014-10-01	11027
2015-01-01	11105
2015-04-01	13177
2015-07-01	11921
2015-10-01	11701
2016-01-01	14302
2016-04-01	16500
2016-07-01	14380
2016-10-01	14824
2017-01-01	16502
2017-04-01	17729
2017-07-01	12845
2017-10-01	16407
2018-01-01	13410
2018-04-01	12822