In order to give a better answer to your question, it might help to better understand the origin of your data. It appears in fact that military expenditure increased during the war; albeit perhaps a bit less than you would expect - you should also be mindful of the fact that Italy was at war (if not under such extreme circumstances as during 1940-43) in 1935-36 as well as 1937-38.

Data of the Italian Tresure - http://www.rgs.mef.gov.it/_Documenti/VERSIONE-I/Pubblicazioni/Studi-e-do/La-spesa-dello-stato/La_spesa_dello_Stato_dall_unit_d_Italia.pdf - provide the following picture for percentage of defense expenses over total expenditure.

year	defense
1910	22.0
1911	24.0
1912	28.9
1913	30.9
1914	46.7
1915	69.8
1916	74.4
1917	70.2
1918	64.0
1919	55.9
1920	34.1
1921	17.5
1922	18.8
1923	21.8
1924	20.1
1925	18.0
1926	20.7
1927	17.9
1928	16.1
1929	19.5
1930	20.6
1931	19.9
1932	21.3
1933	19.2
1934	19.6
1935	19.6
1936	23.1
1937	30.4
1938	31.7
1939	37.3
1940	53.6
1941	58.5
1942	55.2
1943	55.0

As you can see a clear increase in proportion is evident.

For total expenditure, the increase is even more apparent, as the percentage of 1935 has to be computed over a total of 47 billion Euros (2009) as compared to the 27 of the year before. The re-evaluation is clearly necessary as Italy underwent a deflation process during the late 1920s as well as a persistent economical slump the kept going well into the late 1930s.

Data for total expenditure in contemporary values may therefore appear misleading. For instance the 14.2945 million Euros (in contemporary values i.e equal to Lire of the time divided per 1936.27) of 1928 are "equivalent" - in monetary values, not as quota of resources allocated - to 23 billions; while the 13.0281 million Euros of 1934 are equivalent ot over 27.

It also bears the question that military expenditure, military budget and the way econimics looks at agrregated expenditure are not the same thing. If you are looking explicitly for the budget approved year by year; military expenditure in case of War would largely exceed the budget - it also doesn't have to fall entirely within the military expenditure voice in the official data (state participated steel works did not, as far as plant investments went, but military purchases of steel would).

A further source of complication is given by the fact that data for the 1940-43 are not well organized; basically after 1943 the care that the finance administration put into keeping every voice well accounted for proved insufficient for the chaotic nature of war trade. There is a lot of guesswork on the actual expenses of the nation in that time.

Anyways, these are data for all expenses, in 2009 value.

Year	total (Billion Euros 2009)
1910	9.9
1914	15.9
1915	28.2
1916	39.6
1917	42.6
1918	37.9
1919	33.9
1920	23.5
1921	22.1
1922	30.0
1923	32.8
1924	23.2
1925	16.2
1926	15.6
1927	20.4
1928	23.0
1929	19.5
1930	19.8
1931	23.5
1932	22.7
1933	25.6
1934	27.1
1935	47.1
1936	53.8
1937	37.6
1938	34.0
1939	40.0
1940	56.3
1941	65.6
1942	70.1
1943	42.7

Taking this into account. Defense expenditure hit a maximum of roughly 37 Billion Euros (2009) in 1942, compared to roughly 30 Billion Euros (2009) in 1917 - the worst year of WW1 (of course over a different total budget) - and compared to roughly 5.5 Billion Euros (2009) in 1934 - the last full year of peace.