Table 1. Refinement of vocabulary data

Years		Vocabulary categories (d)				Removed vocabulary categories data					Refined vocabulary categories data
		①	②	Total (a)	Frequency	③	④	⑤	Total (b)	Frequency	Total (c)	Frequency
1950s	1958	30	2,386	2,416	4,654	175	1,571	145	1,891	3,135	525	1,519
1980s	1980	41	2,480	2,521	5,021	221	1,786	169	2,176	4,035	345	986
	1982	55	3,276	3,331	6,590	210	2,353	181	2,744	5,122	587	1,468
	1987	67	4,219	4,286	8,631	336	3,041	222	3,599	6,865	687	1,766
	Subtotal	81	6,575	6,656	20,242	567	4,808	276	5,651	16,022	1,005	4,220
1990s	1992	43	4,477	4,520	11,252	330	3,450	281	4,061	10,074	459	1,178
	1999	37	3,726	3,763	9,764	287	2,789	256	3,332	8,729	431	1,035
	Total	57	5,677	5,734	21,016	480	4,202	357	5,039	18,803	695	2,213
2000s	2002	51	3,629	3,680	7,174	285	2,649	229	3,163	5,677	517	1,497
	2004	83	9,333	9,416	18,723	587	7,531	563	8,681	16,633	735	2,090
	Subtotal	101	10,206	10,307	25,897	617	8,122	607	9,346	22,310	961	3,587
2010s	2015	97	5,147	5,244	10,412	721	3,245	741	4,707	8,440	537	1,972
	2019	30	3,990	4,020	8,657	332	2,945	278	3,555	7,517	465	1,140
	Subtotal	113	7,632	7,745	19,069	836	5,183	843	6,862	15,957	883	3,112
Total		382	32,476	32,858	90,878	2,675	23,886	2,228	28,789	76,227	4,069	14,651
Removed repeated duplicate vocabulary categories totals											1,857	14,651